diff --git a/Assets/Scenes/SandboxMain.cs b/Assets/Scenes/SandboxMain.cs
index 459aac0..528040e 100644
--- a/Assets/Scenes/SandboxMain.cs
+++ b/Assets/Scenes/SandboxMain.cs
@@ -17,7 +17,7 @@ public class SandboxMain : MonoBehaviour
 
     CancellationTokenSource cts;
 
-    UniTaskCompletionSource2 ucs;
+    UniTaskCompletionSource ucs;
 
     void Start()
     {
@@ -38,7 +38,7 @@ public class SandboxMain : MonoBehaviour
         Application.logMessageReceived += Application_logMessageReceived;
 
 
-        ucs = new UniTaskCompletionSource2();
+        ucs = new UniTaskCompletionSource();
 
         okButton.onClick.AddListener(async () =>
         {
@@ -60,7 +60,7 @@ public class SandboxMain : MonoBehaviour
         text.text += "\n" + condition;
     }
 
-    async UniTask2 OuterAsync(bool b)
+    async UniTask OuterAsync(bool b)
     {
         UnityEngine.Debug.Log("START OUTER");
 
@@ -72,14 +72,14 @@ public class SandboxMain : MonoBehaviour
         // throw new InvalidOperationException("NAZO ERROR!?"); // error!?
     }
 
-    async UniTask2 InnerAsync(bool b)
+    async UniTask InnerAsync(bool b)
     {
         if (b)
         {
             UnityEngine.Debug.Log("Start delay:" + Time.frameCount);
-            await UniTask2.DelayFrame(60);
+            await UniTask.DelayFrame(60);
             UnityEngine.Debug.Log("End delay:" + Time.frameCount);
-            await UniTask2.DelayFrame(60);
+            await UniTask.DelayFrame(60);
             UnityEngine.Debug.Log("Onemore end delay:" + Time.frameCount);
         }
         else
diff --git a/Assets/UniRx.Async/CompilerServices/AsyncUniTaskMethodBuilder.cs b/Assets/UniRx.Async/CompilerServices/AsyncUniTaskMethodBuilder.cs
index 31f9d34..e53f0f2 100644
--- a/Assets/UniRx.Async/CompilerServices/AsyncUniTaskMethodBuilder.cs
+++ b/Assets/UniRx.Async/CompilerServices/AsyncUniTaskMethodBuilder.cs
@@ -10,274 +10,8 @@ using System.Security;
 
 namespace UniRx.Async.CompilerServices
 {
-    // TODO:Remove
-    public struct AsyncUniTaskMethodBuilder
-    {
-        UniTaskCompletionSource promise;
-        Action moveNext;
-
-        // 1. Static Create method.
-        [DebuggerHidden]
-        public static AsyncUniTaskMethodBuilder Create()
-        {
-            var builder = new AsyncUniTaskMethodBuilder();
-            return builder;
-        }
-
-        // 2. TaskLike Task property.
-        [DebuggerHidden]
-        public UniTask Task
-        {
-            get
-            {
-                if (promise != null)
-                {
-                    return promise.Task;
-                }
-
-                if (moveNext == null)
-                {
-                    return UniTask.CompletedTask;
-                }
-                else
-                {
-                    promise = new UniTaskCompletionSource();
-                    return promise.Task;
-                }
-            }
-        }
-
-        // 3. SetException
-        [DebuggerHidden]
-        public void SetException(Exception exception)
-        {
-            if (promise == null)
-            {
-                promise = new UniTaskCompletionSource();
-            }
-            if (exception is OperationCanceledException ex)
-            {
-                promise.TrySetCanceled(ex);
-            }
-            else
-            {
-                promise.TrySetException(exception);
-            }
-        }
-
-        // 4. SetResult
-        [DebuggerHidden]
-        public void SetResult()
-        {
-            if (moveNext == null)
-            {
-            }
-            else
-            {
-                if (promise == null)
-                {
-                    promise = new UniTaskCompletionSource();
-                }
-                promise.TrySetResult();
-            }
-        }
-
-        // 5. AwaitOnCompleted
-        [DebuggerHidden]
-        public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
-            where TAwaiter : INotifyCompletion
-            where TStateMachine : IAsyncStateMachine
-        {
-            if (moveNext == null)
-            {
-                if (promise == null)
-                {
-                    promise = new UniTaskCompletionSource(); // built future.
-                }
-
-                var runner = new MoveNextRunner<TStateMachine>();
-                moveNext = runner.Run;
-                runner.StateMachine = stateMachine; // set after create delegate.
-            }
-
-            awaiter.OnCompleted(moveNext);
-        }
-
-        // 6. AwaitUnsafeOnCompleted
-        [DebuggerHidden]
-        [SecuritySafeCritical]
-        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
-            where TAwaiter : ICriticalNotifyCompletion
-            where TStateMachine : IAsyncStateMachine
-        {
-            if (moveNext == null)
-            {
-                if (promise == null)
-                {
-                    promise = new UniTaskCompletionSource(); // built future.
-                }
-
-                var runner = new MoveNextRunner<TStateMachine>();
-                moveNext = runner.Run;
-                runner.StateMachine = stateMachine; // set after create delegate.
-            }
-
-            awaiter.UnsafeOnCompleted(moveNext);
-        }
-
-        // 7. Start
-        [DebuggerHidden]
-        public void Start<TStateMachine>(ref TStateMachine stateMachine)
-            where TStateMachine : IAsyncStateMachine
-        {
-            stateMachine.MoveNext();
-        }
-
-        // 8. SetStateMachine
-        [DebuggerHidden]
-        public void SetStateMachine(IAsyncStateMachine stateMachine)
-        {
-        }
-    }
-
-    // TODO:Remove
-    public struct AsyncUniTaskMethodBuilder<T>
-    {
-        T result;
-        UniTaskCompletionSource<T> promise;
-        Action moveNext;
-
-        // 1. Static Create method.
-        [DebuggerHidden]
-        public static AsyncUniTaskMethodBuilder<T> Create()
-        {
-            var builder = new AsyncUniTaskMethodBuilder<T>();
-            return builder;
-        }
-
-        // 2. TaskLike Task property.
-        [DebuggerHidden]
-        public UniTask<T> Task
-        {
-            get
-            {
-                if (promise != null)
-                {
-                    return new UniTask<T>(promise);
-                }
-
-                if (moveNext == null)
-                {
-                    return new UniTask<T>(result);
-                }
-                else
-                {
-                    promise = new UniTaskCompletionSource<T>();
-                    return new UniTask<T>(promise);
-                }
-            }
-        }
-
-        // 3. SetException
-        [DebuggerHidden]
-        public void SetException(Exception exception)
-        {
-            if (promise == null)
-            {
-                promise = new UniTaskCompletionSource<T>();
-            }
-            if (exception is OperationCanceledException ex)
-            {
-                promise.TrySetCanceled(ex);
-            }
-            else
-            {
-                promise.TrySetException(exception);
-            }
-        }
-
-        // 4. SetResult
-        [DebuggerHidden]
-        public void SetResult(T result)
-        {
-            if (moveNext == null)
-            {
-                this.result = result;
-            }
-            else
-            {
-                if (promise == null)
-                {
-                    promise = new UniTaskCompletionSource<T>();
-                }
-                promise.TrySetResult(result);
-            }
-        }
-
-        // 5. AwaitOnCompleted
-        [DebuggerHidden]
-        public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
-            where TAwaiter : INotifyCompletion
-            where TStateMachine : IAsyncStateMachine
-        {
-            if (moveNext == null)
-            {
-                if (promise == null)
-                {
-                    promise = new UniTaskCompletionSource<T>(); // built future.
-                }
-
-                var runner = new MoveNextRunner<TStateMachine>();
-                moveNext = runner.Run;
-                runner.StateMachine = stateMachine; // set after create delegate.
-            }
-
-            awaiter.OnCompleted(moveNext);
-        }
-
-        // 6. AwaitUnsafeOnCompleted
-        [DebuggerHidden]
-        [SecuritySafeCritical]
-        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
-            where TAwaiter : ICriticalNotifyCompletion
-            where TStateMachine : IAsyncStateMachine
-        {
-            if (moveNext == null)
-            {
-                if (promise == null)
-                {
-                    promise = new UniTaskCompletionSource<T>(); // built future.
-                }
-
-                var runner = new MoveNextRunner<TStateMachine>();
-                moveNext = runner.Run;
-                runner.StateMachine = stateMachine; // set after create delegate.
-            }
-
-            awaiter.UnsafeOnCompleted(moveNext);
-        }
-
-        // 7. Start
-        [DebuggerHidden]
-        public void Start<TStateMachine>(ref TStateMachine stateMachine)
-            where TStateMachine : IAsyncStateMachine
-        {
-            stateMachine.MoveNext();
-        }
-
-        // 8. SetStateMachine
-        [DebuggerHidden]
-        public void SetStateMachine(IAsyncStateMachine stateMachine)
-        {
-        }
-    }
-
-
-
-
-
     [StructLayout(LayoutKind.Auto)]
-    public struct AsyncUniTask2MethodBuilder
+    public struct AsyncUniTaskMethodBuilder
     {
         // cache items.
         AutoResetUniTaskCompletionSource promise;
@@ -286,13 +20,13 @@ namespace UniRx.Async.CompilerServices
         // 1. Static Create method.
         [DebuggerHidden]
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static AsyncUniTask2MethodBuilder Create()
+        public static AsyncUniTaskMethodBuilder Create()
         {
             return default;
         }
 
         // 2. TaskLike Task property.
-        public UniTask2 Task
+        public UniTask Task
         {
             [DebuggerHidden]
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -305,7 +39,7 @@ namespace UniRx.Async.CompilerServices
 
                 if (runner == null)
                 {
-                    return UniTask2.CompletedTask;
+                    return UniTask.CompletedTask;
                 }
 
                 promise = AutoResetUniTaskCompletionSource.Create();
@@ -363,7 +97,7 @@ namespace UniRx.Async.CompilerServices
             }
             if (runner == null)
             {
-                runner = MoveNextRunner2<TStateMachine>.Create(ref stateMachine);
+                runner = MoveNextRunner<TStateMachine>.Create(ref stateMachine);
             }
 
             awaiter.OnCompleted(runner.CallMoveNext);
@@ -382,7 +116,7 @@ namespace UniRx.Async.CompilerServices
             }
             if (runner == null)
             {
-                runner = MoveNextRunner2<TStateMachine>.Create(ref stateMachine);
+                runner = MoveNextRunner<TStateMachine>.Create(ref stateMachine);
             }
 
             awaiter.OnCompleted(runner.CallMoveNext);
@@ -405,7 +139,7 @@ namespace UniRx.Async.CompilerServices
     }
 
     [StructLayout(LayoutKind.Auto)]
-    public struct AsyncUniTask2MethodBuilder<T>
+    public struct AsyncUniTaskMethodBuilder<T>
     {
         // cache items.
         AutoResetUniTaskCompletionSource<T> promise;
@@ -415,14 +149,14 @@ namespace UniRx.Async.CompilerServices
         // 1. Static Create method.
         [DebuggerHidden]
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static AsyncUniTask2MethodBuilder<T> Create()
+        public static AsyncUniTaskMethodBuilder<T> Create()
         {
             return default;
         }
 
         // 2. TaskLike Task property.
         [DebuggerHidden]
-        public UniTask2<T> Task
+        public UniTask<T> Task
         {
             get
             {
@@ -433,7 +167,7 @@ namespace UniRx.Async.CompilerServices
 
                 if (runner == null)
                 {
-                    return UniTask2.FromResult(result);
+                    return UniTask.FromResult(result);
                 }
 
                 promise = AutoResetUniTaskCompletionSource<T>.Create();
@@ -494,7 +228,7 @@ namespace UniRx.Async.CompilerServices
             }
             if (runner == null)
             {
-                runner = MoveNextRunner2<TStateMachine>.Create(ref stateMachine);
+                runner = MoveNextRunner<TStateMachine>.Create(ref stateMachine);
             }
 
             awaiter.OnCompleted(runner.CallMoveNext);
@@ -513,7 +247,7 @@ namespace UniRx.Async.CompilerServices
             }
             if (runner == null)
             {
-                runner = MoveNextRunner2<TStateMachine>.Create(ref stateMachine);
+                runner = MoveNextRunner<TStateMachine>.Create(ref stateMachine);
             }
 
             awaiter.OnCompleted(runner.CallMoveNext);
diff --git a/Assets/UniRx.Async/CompilerServices/AsyncUniTaskVoidMethodBuilder.cs b/Assets/UniRx.Async/CompilerServices/AsyncUniTaskVoidMethodBuilder.cs
index 9fad249..2a3b43f 100644
--- a/Assets/UniRx.Async/CompilerServices/AsyncUniTaskVoidMethodBuilder.cs
+++ b/Assets/UniRx.Async/CompilerServices/AsyncUniTaskVoidMethodBuilder.cs
@@ -66,7 +66,7 @@ namespace UniRx.Async.CompilerServices
         {
             if (runner == null)
             {
-                runner = MoveNextRunner2<TStateMachine>.Create(ref stateMachine);
+                runner = MoveNextRunner<TStateMachine>.Create(ref stateMachine);
             }
 
             awaiter.OnCompleted(runner.CallMoveNext);
@@ -81,7 +81,7 @@ namespace UniRx.Async.CompilerServices
         {
             if (runner == null)
             {
-                runner = MoveNextRunner2<TStateMachine>.Create(ref stateMachine);
+                runner = MoveNextRunner<TStateMachine>.Create(ref stateMachine);
             }
 
             awaiter.OnCompleted(runner.CallMoveNext);
diff --git a/Assets/UniRx.Async/CompilerServices/MoveNextRunner.cs b/Assets/UniRx.Async/CompilerServices/MoveNextRunner.cs
index 7c7155f..365ca79 100644
--- a/Assets/UniRx.Async/CompilerServices/MoveNextRunner.cs
+++ b/Assets/UniRx.Async/CompilerServices/MoveNextRunner.cs
@@ -9,43 +9,30 @@ using UniRx.Async.Internal;
 
 namespace UniRx.Async.CompilerServices
 {
-    // TODO: Remove it.
-    internal class MoveNextRunner<TStateMachine>
-        where TStateMachine : IAsyncStateMachine
-    {
-        public TStateMachine StateMachine;
-
-        [DebuggerHidden]
-        public void Run()
-        {
-            StateMachine.MoveNext();
-        }
-    }
-
     internal interface IMoveNextRunner
     {
         Action CallMoveNext { get; }
         void Return();
     }
 
-    internal class MoveNextRunner2<TStateMachine> : IMoveNextRunner, IPromisePoolItem
+    internal class MoveNextRunner<TStateMachine> : IMoveNextRunner, IPromisePoolItem
         where TStateMachine : IAsyncStateMachine
     {
-        static PromisePool<MoveNextRunner2<TStateMachine>> pool = new PromisePool<MoveNextRunner2<TStateMachine>>();
+        static PromisePool<MoveNextRunner<TStateMachine>> pool = new PromisePool<MoveNextRunner<TStateMachine>>();
 
         TStateMachine stateMachine;
         internal readonly Action callMoveNext;
 
         public Action CallMoveNext => callMoveNext;
 
-        MoveNextRunner2()
+        MoveNextRunner()
         {
             callMoveNext = MoveNext;
         }
 
-        public static MoveNextRunner2<TStateMachine> Create(ref TStateMachine stateMachine)
+        public static MoveNextRunner<TStateMachine> Create(ref TStateMachine stateMachine)
         {
-            var result = pool.TryRent() ?? new MoveNextRunner2<TStateMachine>();
+            var result = pool.TryRent() ?? new MoveNextRunner<TStateMachine>();
             result.stateMachine = stateMachine;
             return result;
         }
diff --git a/Assets/UniRx.Async/UniTask.Bridge.cs b/Assets/UniRx.Async/UniTask.Bridge.cs
index a9ecbf6..814bd02 100644
--- a/Assets/UniRx.Async/UniTask.Bridge.cs
+++ b/Assets/UniRx.Async/UniTask.Bridge.cs
@@ -8,14 +8,6 @@ namespace UniRx.Async
 {
     // UnityEngine Bridges.
 
-    public partial struct UniTask2
-    {
-        public static IEnumerator ToCoroutine(Func<UniTask2> taskFactory)
-        {
-            return taskFactory().ToCoroutine();
-        }
-    }
-
     public partial struct UniTask
     {
         public static IEnumerator ToCoroutine(Func<UniTask> taskFactory)
diff --git a/Assets/UniRx.Async/UniTask.Delay.cs b/Assets/UniRx.Async/UniTask.Delay.cs
index 25e8b5f..0ab0fb2 100644
--- a/Assets/UniRx.Async/UniTask.Delay.cs
+++ b/Assets/UniRx.Async/UniTask.Delay.cs
@@ -9,31 +9,30 @@ using UnityEngine;
 
 namespace UniRx.Async
 {
-    // TODO:rename
-    public partial struct UniTask2
+    public partial struct UniTask
     {
-        public static YieldAwaitable2 Yield(PlayerLoopTiming timing = PlayerLoopTiming.Update)
+        public static YieldAwaitable Yield(PlayerLoopTiming timing = PlayerLoopTiming.Update)
         {
             // optimized for single continuation
-            return new YieldAwaitable2(timing);
+            return new YieldAwaitable(timing);
         }
 
-        public static UniTask2 Yield(PlayerLoopTiming timing, CancellationToken cancellationToken)
+        public static UniTask Yield(PlayerLoopTiming timing, CancellationToken cancellationToken)
         {
-            return new UniTask2(YieldPromise.Create(timing, cancellationToken, out var token), token);
+            return new UniTask(YieldPromise.Create(timing, cancellationToken, out var token), token);
         }
 
-        public static UniTask2 DelayFrame(int delayFrameCount, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
+        public static UniTask DelayFrame(int delayFrameCount, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
         {
             if (delayFrameCount < 0)
             {
                 throw new ArgumentOutOfRangeException("Delay does not allow minus delayFrameCount. delayFrameCount:" + delayFrameCount);
             }
 
-            return new UniTask2(DelayFramePromise.Create(delayFrameCount, delayTiming, cancellationToken, out var token), token);
+            return new UniTask(DelayFramePromise.Create(delayFrameCount, delayTiming, cancellationToken, out var token), token);
         }
 
-        public static UniTask2 Delay(int millisecondsDelay, bool ignoreTimeScale = false, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
+        public static UniTask Delay(int millisecondsDelay, bool ignoreTimeScale = false, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
         {
             var delayTimeSpan = TimeSpan.FromMilliseconds(millisecondsDelay);
             if (delayTimeSpan < TimeSpan.Zero)
@@ -42,11 +41,11 @@ namespace UniRx.Async
             }
 
             return (ignoreTimeScale)
-                ? new UniTask2(DelayIgnoreTimeScalePromise.Create(delayTimeSpan, delayTiming, cancellationToken, out var token), token)
-                : new UniTask2(DelayPromise.Create(delayTimeSpan, delayTiming, cancellationToken, out token), token);
+                ? new UniTask(DelayIgnoreTimeScalePromise.Create(delayTimeSpan, delayTiming, cancellationToken, out var token), token)
+                : new UniTask(DelayPromise.Create(delayTimeSpan, delayTiming, cancellationToken, out token), token);
         }
 
-        public static UniTask2 Delay(TimeSpan delayTimeSpan, bool ignoreTimeScale = false, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
+        public static UniTask Delay(TimeSpan delayTimeSpan, bool ignoreTimeScale = false, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
         {
             if (delayTimeSpan < TimeSpan.Zero)
             {
@@ -54,8 +53,8 @@ namespace UniRx.Async
             }
 
             return (ignoreTimeScale)
-                ? new UniTask2(DelayIgnoreTimeScalePromise.Create(delayTimeSpan, delayTiming, cancellationToken, out var token), token)
-                : new UniTask2(DelayPromise.Create(delayTimeSpan, delayTiming, cancellationToken, out token), token);
+                ? new UniTask(DelayIgnoreTimeScalePromise.Create(delayTimeSpan, delayTiming, cancellationToken, out var token), token)
+                : new UniTask(DelayPromise.Create(delayTimeSpan, delayTiming, cancellationToken, out token), token);
         }
 
         class YieldPromise : IUniTaskSource, IPlayerLoopItem, IPromisePoolItem
@@ -405,244 +404,6 @@ namespace UniRx.Async
         }
     }
 
-    // TODO:rename
-    public struct YieldAwaitable2
-    {
-        readonly PlayerLoopTiming timing;
-
-        public YieldAwaitable2(PlayerLoopTiming timing)
-        {
-            this.timing = timing;
-        }
-
-        public Awaiter GetAwaiter()
-        {
-            return new Awaiter(timing);
-        }
-
-        public UniTask2 ToUniTask()
-        {
-            return UniTask2.Yield(timing, CancellationToken.None);
-        }
-
-        public struct Awaiter : ICriticalNotifyCompletion
-        {
-            readonly PlayerLoopTiming timing;
-
-            public Awaiter(PlayerLoopTiming timing)
-            {
-                this.timing = timing;
-            }
-
-            public bool IsCompleted => false;
-
-            public void GetResult() { }
-
-            public void OnCompleted(Action continuation)
-            {
-                PlayerLoopHelper.AddContinuation(timing, continuation);
-            }
-
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                PlayerLoopHelper.AddContinuation(timing, continuation);
-            }
-        }
-    }
-
-
-    // TODO:remove
-    public partial struct UniTask
-    {
-        public static YieldAwaitable Yield(PlayerLoopTiming timing = PlayerLoopTiming.Update)
-        {
-            // optimized for single continuation
-            return new YieldAwaitable(timing);
-        }
-
-        public static UniTask Yield(PlayerLoopTiming timing, CancellationToken cancellationToken)
-        {
-            return new UniTask(new YieldPromise(timing, cancellationToken));
-        }
-
-        public static UniTask<int> DelayFrame(int delayFrameCount, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
-        {
-            if (delayFrameCount < 0)
-            {
-                throw new ArgumentOutOfRangeException("Delay does not allow minus delayFrameCount. delayFrameCount:" + delayFrameCount);
-            }
-
-            var source = new DelayFramePromise(delayFrameCount, delayTiming, cancellationToken);
-            return source.Task;
-        }
-
-        public static UniTask Delay(int millisecondsDelay, bool ignoreTimeScale = false, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
-        {
-            var delayTimeSpan = TimeSpan.FromMilliseconds(millisecondsDelay);
-            if (delayTimeSpan < TimeSpan.Zero)
-            {
-                throw new ArgumentOutOfRangeException("Delay does not allow minus delayFrameCount. delayTimeSpan:" + delayTimeSpan);
-            }
-
-            return (ignoreTimeScale)
-                ? new DelayIgnoreTimeScalePromise(delayTimeSpan, delayTiming, cancellationToken).Task
-                : new DelayPromise(delayTimeSpan, delayTiming, cancellationToken).Task;
-        }
-
-        public static UniTask Delay(TimeSpan delayTimeSpan, bool ignoreTimeScale = false, PlayerLoopTiming delayTiming = PlayerLoopTiming.Update, CancellationToken cancellationToken = default(CancellationToken))
-        {
-            if (delayTimeSpan < TimeSpan.Zero)
-            {
-                throw new ArgumentOutOfRangeException("Delay does not allow minus delayFrameCount. delayTimeSpan:" + delayTimeSpan);
-            }
-
-            return (ignoreTimeScale)
-                ? new DelayIgnoreTimeScalePromise(delayTimeSpan, delayTiming, cancellationToken).Task
-                : new DelayPromise(delayTimeSpan, delayTiming, cancellationToken).Task;
-        }
-
-        class YieldPromise : PlayerLoopReusablePromiseBase
-        {
-            public YieldPromise(PlayerLoopTiming timing, CancellationToken cancellationToken)
-                : base(timing, cancellationToken, 2)
-            {
-            }
-
-            protected override void OnRunningStart()
-            {
-            }
-
-            public override bool MoveNext()
-            {
-                Complete();
-                if (cancellationToken.IsCancellationRequested)
-                {
-                    TrySetCanceled();
-                }
-                else
-                {
-                    TrySetResult();
-                }
-
-                return false;
-            }
-        }
-
-        class DelayFramePromise : PlayerLoopReusablePromiseBase<int>
-        {
-            readonly int delayFrameCount;
-            int currentFrameCount;
-
-            public DelayFramePromise(int delayFrameCount, PlayerLoopTiming timing, CancellationToken cancellationToken)
-                : base(timing, cancellationToken, 2)
-            {
-                this.delayFrameCount = delayFrameCount;
-                this.currentFrameCount = 0;
-            }
-
-            protected override void OnRunningStart()
-            {
-                currentFrameCount = 0;
-            }
-
-            public override bool MoveNext()
-            {
-                if (cancellationToken.IsCancellationRequested)
-                {
-                    Complete();
-                    TrySetCanceled();
-                    return false;
-                }
-
-                if (currentFrameCount == delayFrameCount)
-                {
-                    Complete();
-                    TrySetResult(currentFrameCount);
-                    return false;
-                }
-
-                currentFrameCount++;
-                return true;
-            }
-        }
-
-        class DelayPromise : PlayerLoopReusablePromiseBase
-        {
-            readonly float delayFrameTimeSpan;
-            float elapsed;
-
-            public DelayPromise(TimeSpan delayFrameTimeSpan, PlayerLoopTiming timing, CancellationToken cancellationToken)
-                : base(timing, cancellationToken, 2)
-            {
-                this.delayFrameTimeSpan = (float)delayFrameTimeSpan.TotalSeconds;
-            }
-
-            protected override void OnRunningStart()
-            {
-                this.elapsed = 0.0f;
-            }
-
-            public override bool MoveNext()
-            {
-                if (cancellationToken.IsCancellationRequested)
-                {
-                    Complete();
-                    TrySetCanceled();
-                    return false;
-                }
-
-                elapsed += Time.deltaTime;
-                if (elapsed >= delayFrameTimeSpan)
-                {
-                    Complete();
-                    TrySetResult();
-                    return false;
-                }
-
-                return true;
-            }
-        }
-
-        class DelayIgnoreTimeScalePromise : PlayerLoopReusablePromiseBase
-        {
-            readonly float delayFrameTimeSpan;
-            float elapsed;
-
-            public DelayIgnoreTimeScalePromise(TimeSpan delayFrameTimeSpan, PlayerLoopTiming timing, CancellationToken cancellationToken)
-                : base(timing, cancellationToken, 2)
-            {
-                this.delayFrameTimeSpan = (float)delayFrameTimeSpan.TotalSeconds;
-            }
-
-            protected override void OnRunningStart()
-            {
-                this.elapsed = 0.0f;
-            }
-
-            public override bool MoveNext()
-            {
-                if (cancellationToken.IsCancellationRequested)
-                {
-                    Complete();
-                    TrySetCanceled();
-                    return false;
-                }
-
-                elapsed += Time.unscaledDeltaTime;
-
-                if (elapsed >= delayFrameTimeSpan)
-                {
-                    Complete();
-                    TrySetResult();
-                    return false;
-                }
-
-                return true;
-            }
-        }
-    }
-
-    // TODO:remove
     public struct YieldAwaitable
     {
         readonly PlayerLoopTiming timing;
diff --git a/Assets/UniRx.Async/UniTask.Factory.cs b/Assets/UniRx.Async/UniTask.Factory.cs
index 9893ad2..e97d36e 100644
--- a/Assets/UniRx.Async/UniTask.Factory.cs
+++ b/Assets/UniRx.Async/UniTask.Factory.cs
@@ -7,11 +7,11 @@ using UnityEngine.Events;
 
 namespace UniRx.Async
 {
-    public partial struct UniTask2
+    public partial struct UniTask
     {
-        static readonly UniTask2 CanceledUniTask = new Func<UniTask2>(() =>
+        static readonly UniTask CanceledUniTask = new Func<UniTask>(() =>
         {
-            var promise = new UniTaskCompletionSource2();
+            var promise = new UniTaskCompletionSource();
             promise.SetCanceled(CancellationToken.None);
             promise.MarkHandled();
             return promise.Task;
@@ -19,41 +19,41 @@ namespace UniRx.Async
 
         static class CanceledUniTaskCache<T>
         {
-            public static readonly UniTask2<T> Task;
+            public static readonly UniTask<T> Task;
 
             static CanceledUniTaskCache()
             {
-                var promise = new UniTaskCompletionSource2<T>();
+                var promise = new UniTaskCompletionSource<T>();
                 promise.SetCanceled(CancellationToken.None);
                 promise.MarkHandled();
                 Task = promise.Task;
             }
         }
 
-        public static readonly UniTask2 CompletedTask = new UniTask2();
+        public static readonly UniTask CompletedTask = new UniTask();
 
-        public static UniTask2 FromException(Exception ex)
+        public static UniTask FromException(Exception ex)
         {
-            var promise = new UniTaskCompletionSource2();
+            var promise = new UniTaskCompletionSource();
             promise.SetException(ex);
             promise.MarkHandled();
             return promise.Task;
         }
 
-        public static UniTask2<T> FromException<T>(Exception ex)
+        public static UniTask<T> FromException<T>(Exception ex)
         {
-            var promise = new UniTaskCompletionSource2<T>();
+            var promise = new UniTaskCompletionSource<T>();
             promise.SetException(ex);
             promise.MarkHandled();
             return promise.Task;
         }
 
-        public static UniTask2<T> FromResult<T>(T value)
+        public static UniTask<T> FromResult<T>(T value)
         {
-            return new UniTask2<T>(value);
+            return new UniTask<T>(value);
         }
 
-        public static UniTask2 FromCanceled(CancellationToken cancellationToken = default)
+        public static UniTask FromCanceled(CancellationToken cancellationToken = default)
         {
             if (cancellationToken == CancellationToken.None)
             {
@@ -61,14 +61,14 @@ namespace UniRx.Async
             }
             else
             {
-                var promise = new UniTaskCompletionSource2();
+                var promise = new UniTaskCompletionSource();
                 promise.SetCanceled(cancellationToken);
                 promise.MarkHandled();
                 return promise.Task;
             }
         }
 
-        public static UniTask2<T> FromCanceled<T>(CancellationToken cancellationToken = default)
+        public static UniTask<T> FromCanceled<T>(CancellationToken cancellationToken = default)
         {
             if (cancellationToken == CancellationToken.None)
             {
@@ -76,7 +76,7 @@ namespace UniRx.Async
             }
             else
             {
-                var promise = new UniTaskCompletionSource2<T>();
+                var promise = new UniTaskCompletionSource<T>();
                 promise.SetCanceled(cancellationToken);
                 promise.MarkHandled();
                 return promise.Task;
@@ -120,143 +120,15 @@ namespace UniRx.Async
         }
     }
 
-
-    // TODO:remove
-    public partial struct UniTask
-    {
-        static readonly UniTask CanceledUniTask = new Func<UniTask>(() =>
-        {
-            var promise = new UniTaskCompletionSource<AsyncUnit>();
-            promise.TrySetCanceled();
-            promise.MarkHandled();
-            return new UniTask(promise);
-        })();
-
-        public static UniTask CompletedTask
-        {
-            get
-            {
-                return new UniTask();
-            }
-        }
-
-        public static UniTask FromException(Exception ex)
-        {
-            var promise = new UniTaskCompletionSource<AsyncUnit>();
-            promise.TrySetException(ex);
-            promise.MarkHandled();
-            return new UniTask(promise);
-        }
-
-        public static UniTask<T> FromException<T>(Exception ex)
-        {
-            var promise = new UniTaskCompletionSource<T>();
-            promise.TrySetException(ex);
-            promise.MarkHandled();
-            return new UniTask<T>(promise);
-        }
-
-        public static UniTask<T> FromResult<T>(T value)
-        {
-            return new UniTask<T>(value);
-        }
-
-        public static UniTask FromCanceled()
-        {
-            return CanceledUniTask;
-        }
-
-        public static UniTask<T> FromCanceled<T>()
-        {
-            return CanceledUniTaskCache<T>.Task;
-        }
-
-        public static UniTask FromCanceled(CancellationToken token)
-        {
-            var promise = new UniTaskCompletionSource<AsyncUnit>();
-            promise.TrySetException(new OperationCanceledException(token));
-            promise.MarkHandled();
-            return new UniTask(promise);
-        }
-
-        public static UniTask<T> FromCanceled<T>(CancellationToken token)
-        {
-            var promise = new UniTaskCompletionSource<T>();
-            promise.TrySetException(new OperationCanceledException(token));
-            promise.MarkHandled();
-            return new UniTask<T>(promise);
-        }
-
-        /// <summary>shorthand of new UniTask[T](Func[UniTask[T]] factory)</summary>
-        public static UniTask<T> Lazy<T>(Func<UniTask<T>> factory)
-        {
-            return new UniTask<T>(factory);
-        }
-
-        /// <summary>
-        /// helper of create add UniTaskVoid to delegate.
-        /// For example: FooEvent += () => UniTask.Void(async () => { /* */ })
-        /// </summary>
-        public static void Void(Func<UniTask> asyncAction)
-        {
-            asyncAction().Forget();
-        }
-
-        public static Action VoidAction(Func<UniTask> asyncAction)
-        {
-            return () => Void(asyncAction);
-        }
-
-        public static UnityAction VoidUnityAction(Func<UniTask> asyncAction)
-        {
-            return () => Void(asyncAction);
-        }
-
-        /// <summary>
-        /// helper of create add UniTaskVoid to delegate.
-        /// For example: FooEvent += (sender, e) => UniTask.Void(async arg => { /* */ }, (sender, e))
-        /// </summary>
-        public static void Void<T>(Func<T, UniTask> asyncAction, T state)
-        {
-            asyncAction(state).Forget();
-        }
-
-        static class CanceledUniTaskCache<T>
-        {
-            public static readonly UniTask<T> Task;
-
-            static CanceledUniTaskCache()
-            {
-                var promise = new UniTaskCompletionSource<T>();
-                promise.TrySetCanceled();
-                promise.MarkHandled();
-                Task = new UniTask<T>(promise);
-            }
-        }
-    }
-
-
-    // TODO:remove
     internal static class CompletedTasks
     {
+        public static readonly UniTask Completed = new UniTask();
+        public static readonly UniTask<AsyncUnit> AsyncUnit = UniTask.FromResult(UniRx.Async.AsyncUnit.Default);
         public static readonly UniTask<bool> True = UniTask.FromResult(true);
         public static readonly UniTask<bool> False = UniTask.FromResult(false);
         public static readonly UniTask<int> Zero = UniTask.FromResult(0);
         public static readonly UniTask<int> MinusOne = UniTask.FromResult(-1);
         public static readonly UniTask<int> One = UniTask.FromResult(1);
     }
-
-
-    // TODO:rename
-    internal static class CompletedTasks2
-    {
-        public static readonly UniTask2 Completed = new UniTask2();
-        public static readonly UniTask2<AsyncUnit> AsyncUnit = UniTask2.FromResult(UniRx.Async.AsyncUnit.Default);
-        public static readonly UniTask2<bool> True = UniTask2.FromResult(true);
-        public static readonly UniTask2<bool> False = UniTask2.FromResult(false);
-        public static readonly UniTask2<int> Zero = UniTask2.FromResult(0);
-        public static readonly UniTask2<int> MinusOne = UniTask2.FromResult(-1);
-        public static readonly UniTask2<int> One = UniTask2.FromResult(1);
-    }
 }
 #endif
\ No newline at end of file
diff --git a/Assets/UniRx.Async/UniTask.cs b/Assets/UniRx.Async/UniTask.cs
index bf71764..1b97d18 100644
--- a/Assets/UniRx.Async/UniTask.cs
+++ b/Assets/UniRx.Async/UniTask.cs
@@ -25,15 +25,15 @@ namespace UniRx.Async
     /// <summary>
     /// Lightweight unity specified task-like object.
     /// </summary>
-    [AsyncMethodBuilder(typeof(AsyncUniTask2MethodBuilder))]
-    public readonly partial struct UniTask2
+    [AsyncMethodBuilder(typeof(AsyncUniTaskMethodBuilder))]
+    public readonly partial struct UniTask
     {
         readonly IUniTaskSource source;
         readonly short token;
 
         [DebuggerHidden]
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public UniTask2(IUniTaskSource source, short token)
+        public UniTask(IUniTaskSource source, short token)
         {
             this.source = source;
             this.token = token;
@@ -60,12 +60,12 @@ namespace UniRx.Async
         /// <summary>
         /// returns (bool IsCanceled) instead of throws OperationCanceledException.
         /// </summary>
-        public UniTask2<bool> SuppressCancellationThrow()
+        public UniTask<bool> SuppressCancellationThrow()
         {
             var status = Status;
-            if (status == AwaiterStatus.Succeeded) return CompletedTasks2.False;
-            if (status == AwaiterStatus.Canceled) return CompletedTasks2.True;
-            return new UniTask2<bool>(new IsCanceledSource(source), token);
+            if (status == AwaiterStatus.Succeeded) return CompletedTasks.False;
+            if (status == AwaiterStatus.Canceled) return CompletedTasks.True;
+            return new UniTask<bool>(new IsCanceledSource(source), token);
         }
 
         public override string ToString()
@@ -77,7 +77,7 @@ namespace UniRx.Async
         /// <summary>
         /// Memoizing inner IValueTaskSource. The result UniTask can await multiple.
         /// </summary>
-        public UniTask2 Preserve()
+        public UniTask Preserve()
         {
             if (source == null)
             {
@@ -85,21 +85,21 @@ namespace UniRx.Async
             }
             else
             {
-                return new UniTask2(new MemoizeSource(source), token);
+                return new UniTask(new MemoizeSource(source), token);
             }
         }
 
-        public static implicit operator UniTask2<AsyncUnit>(UniTask2 task)
+        public static implicit operator UniTask<AsyncUnit>(UniTask task)
         {
-            if (task.source == null) return CompletedTasks2.AsyncUnit;
+            if (task.source == null) return CompletedTasks.AsyncUnit;
 
             var status = task.source.GetStatus(task.token);
             if (status.IsCompletedSuccessfully())
             {
-                return CompletedTasks2.AsyncUnit;
+                return CompletedTasks.AsyncUnit;
             }
 
-            return new UniTask2<AsyncUnit>(new AsyncUnitSource(task.source), task.token);
+            return new UniTask<AsyncUnit>(new AsyncUnitSource(task.source), task.token);
         }
 
         class AsyncUnitSource : IUniTaskSource<AsyncUnit>
@@ -261,11 +261,11 @@ namespace UniRx.Async
 
         public readonly struct Awaiter : ICriticalNotifyCompletion
         {
-            readonly UniTask2 task;
+            readonly UniTask task;
 
             [DebuggerHidden]
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public Awaiter(in UniTask2 task)
+            public Awaiter(in UniTask task)
             {
                 this.task = task;
             }
@@ -336,8 +336,8 @@ namespace UniRx.Async
     /// <summary>
     /// Lightweight unity specified task-like object.
     /// </summary>
-    [AsyncMethodBuilder(typeof(AsyncUniTask2MethodBuilder<>))]
-    public readonly struct UniTask2<T>
+    [AsyncMethodBuilder(typeof(AsyncUniTaskMethodBuilder<>))]
+    public readonly struct UniTask<T>
     {
         readonly IUniTaskSource<T> source;
         readonly T result;
@@ -345,7 +345,7 @@ namespace UniRx.Async
 
         [DebuggerHidden]
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public UniTask2(T result)
+        public UniTask(T result)
         {
             this.source = default;
             this.token = default;
@@ -354,7 +354,7 @@ namespace UniRx.Async
 
         [DebuggerHidden]
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public UniTask2(IUniTaskSource<T> source, short token)
+        public UniTask(IUniTaskSource<T> source, short token)
         {
             this.source = source;
             this.token = token;
@@ -381,7 +381,7 @@ namespace UniRx.Async
         /// <summary>
         /// Memoizing inner IValueTaskSource. The result UniTask can await multiple.
         /// </summary>
-        public UniTask2<T> Preserve()
+        public UniTask<T> Preserve()
         {
             if (source == null)
             {
@@ -389,34 +389,34 @@ namespace UniRx.Async
             }
             else
             {
-                return new UniTask2<T>(new MemoizeSource(source), token);
+                return new UniTask<T>(new MemoizeSource(source), token);
             }
         }
 
-        public static implicit operator UniTask2(UniTask2<T> task)
+        public static implicit operator UniTask(UniTask<T> task)
         {
-            if (task.source == null) return UniTask2.CompletedTask;
+            if (task.source == null) return UniTask.CompletedTask;
 
             var status = task.source.GetStatus(task.token);
             if (status.IsCompletedSuccessfully())
             {
-                return UniTask2.CompletedTask;
+                return UniTask.CompletedTask;
             }
 
-            return new UniTask2(task.source, task.token);
+            return new UniTask(task.source, task.token);
         }
 
         /// <summary>
         /// returns (bool IsCanceled, T Result) instead of throws OperationCanceledException.
         /// </summary>
-        public UniTask2<(bool IsCanceled, T Result)> SuppressCancellationThrow()
+        public UniTask<(bool IsCanceled, T Result)> SuppressCancellationThrow()
         {
             if (source == null)
             {
-                return new UniTask2<(bool IsCanceled, T Result)>((false, result));
+                return new UniTask<(bool IsCanceled, T Result)>((false, result));
             }
 
-            return new UniTask2<(bool, T)>(new IsCanceledSource(source), token);
+            return new UniTask<(bool, T)>(new IsCanceledSource(source), token);
         }
 
         public override string ToString()
@@ -568,11 +568,11 @@ namespace UniRx.Async
 
         public readonly struct Awaiter : ICriticalNotifyCompletion
         {
-            readonly UniTask2<T> task;
+            readonly UniTask<T> task;
 
             [DebuggerHidden]
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public Awaiter(in UniTask2<T> task)
+            public Awaiter(in UniTask<T> task)
             {
                 this.task = task;
             }
@@ -649,472 +649,6 @@ namespace UniRx.Async
             }
         }
     }
-
-
-    /// <summary>
-    /// Lightweight unity specified task-like object.
-    /// </summary>
-    [AsyncMethodBuilder(typeof(AsyncUniTaskMethodBuilder))]
-    public partial struct UniTask : IEquatable<UniTask>
-    {
-        static readonly UniTask<AsyncUnit> DefaultAsyncUnitTask = new UniTask<AsyncUnit>(AsyncUnit.Default);
-
-        readonly IAwaiter awaiter;
-
-        [DebuggerHidden]
-        public UniTask(IAwaiter awaiter)
-        {
-            this.awaiter = awaiter;
-        }
-
-        [DebuggerHidden]
-        public UniTask(Func<UniTask> factory)
-        {
-            this.awaiter = new LazyPromise(factory);
-        }
-
-        [DebuggerHidden]
-        public AwaiterStatus Status
-        {
-            get
-            {
-                return awaiter == null ? AwaiterStatus.Succeeded : awaiter.Status;
-            }
-        }
-
-        [DebuggerHidden]
-        public bool IsCompleted
-        {
-            get
-            {
-                return awaiter == null ? true : awaiter.IsCompleted;
-            }
-        }
-
-        [DebuggerHidden]
-        public void GetResult()
-        {
-            if (awaiter != null)
-            {
-                awaiter.GetResult();
-            }
-        }
-
-        [DebuggerHidden]
-        public Awaiter GetAwaiter()
-        {
-            return new Awaiter(this);
-        }
-
-        /// <summary>
-        /// returns (bool IsCanceled) instead of throws OperationCanceledException.
-        /// </summary>
-        public UniTask<bool> SuppressCancellationThrow()
-        {
-            var status = Status;
-            if (status == AwaiterStatus.Succeeded) return CompletedTasks.False;
-            if (status == AwaiterStatus.Canceled) return CompletedTasks.True;
-            return new UniTask<bool>(new IsCanceledAwaiter(awaiter));
-        }
-
-        public bool Equals(UniTask other)
-        {
-            if (this.awaiter == null && other.awaiter == null)
-            {
-                return true;
-            }
-            else if (this.awaiter != null && other.awaiter != null)
-            {
-                return this.awaiter == other.awaiter;
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        public override int GetHashCode()
-        {
-            if (this.awaiter == null)
-            {
-                return 0;
-            }
-            else
-            {
-                return this.awaiter.GetHashCode();
-            }
-        }
-
-        public override string ToString()
-        {
-            return (this.awaiter == null) ? "()"
-                 : (this.awaiter.Status == AwaiterStatus.Succeeded) ? "()"
-                 : "(" + this.awaiter.Status + ")";
-        }
-
-        public static implicit operator UniTask<AsyncUnit>(UniTask task)
-        {
-            if (task.awaiter != null)
-            {
-                if (task.awaiter.IsCompleted)
-                {
-                    return DefaultAsyncUnitTask;
-                }
-                else
-                {
-                    // UniTask<T> -> UniTask is free but UniTask -> UniTask<T> requires wrapping cost.
-                    return new UniTask<AsyncUnit>(new AsyncUnitAwaiter(task.awaiter));
-                }
-            }
-            else
-            {
-                return DefaultAsyncUnitTask;
-            }
-        }
-
-        class AsyncUnitAwaiter : IAwaiter<AsyncUnit>
-        {
-            readonly IAwaiter awaiter;
-
-            public AsyncUnitAwaiter(IAwaiter awaiter)
-            {
-                this.awaiter = awaiter;
-            }
-
-            public bool IsCompleted => awaiter.IsCompleted;
-
-            public AwaiterStatus Status => awaiter.Status;
-
-            public AsyncUnit GetResult()
-            {
-                awaiter.GetResult();
-                return AsyncUnit.Default;
-            }
-
-            public void OnCompleted(Action continuation)
-            {
-                awaiter.OnCompleted(continuation);
-            }
-
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                awaiter.UnsafeOnCompleted(continuation);
-            }
-
-            void IAwaiter.GetResult()
-            {
-                awaiter.GetResult();
-            }
-        }
-
-        class IsCanceledAwaiter : IAwaiter<bool>
-        {
-            readonly IAwaiter awaiter;
-
-            public IsCanceledAwaiter(IAwaiter awaiter)
-            {
-                this.awaiter = awaiter;
-            }
-
-            public bool IsCompleted => awaiter.IsCompleted;
-
-            public AwaiterStatus Status => awaiter.Status;
-
-            public bool GetResult()
-            {
-                if (awaiter.Status == AwaiterStatus.Canceled)
-                {
-                    return true;
-                }
-                awaiter.GetResult();
-                return false;
-            }
-
-            public void OnCompleted(Action continuation)
-            {
-                awaiter.OnCompleted(continuation);
-            }
-
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                awaiter.UnsafeOnCompleted(continuation);
-            }
-
-            void IAwaiter.GetResult()
-            {
-                awaiter.GetResult();
-            }
-        }
-
-        public struct Awaiter : IAwaiter
-        {
-            readonly UniTask task;
-
-            [DebuggerHidden]
-            public Awaiter(UniTask task)
-            {
-                this.task = task;
-            }
-
-            [DebuggerHidden]
-            public bool IsCompleted => task.IsCompleted;
-
-            [DebuggerHidden]
-            public AwaiterStatus Status => task.Status;
-
-            [DebuggerHidden]
-            public void GetResult() => task.GetResult();
-
-            [DebuggerHidden]
-            public void OnCompleted(Action continuation)
-            {
-                if (task.awaiter != null)
-                {
-                    task.awaiter.OnCompleted(continuation);
-                }
-                else
-                {
-                    continuation();
-                }
-            }
-
-            [DebuggerHidden]
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                if (task.awaiter != null)
-                {
-                    task.awaiter.UnsafeOnCompleted(continuation);
-                }
-                else
-                {
-                    continuation();
-                }
-            }
-        }
-    }
-
-    /// <summary>
-    /// Lightweight unity specified task-like object.
-    /// </summary>
-    [AsyncMethodBuilder(typeof(AsyncUniTaskMethodBuilder<>))]
-    public struct UniTask<T> : IEquatable<UniTask<T>>
-    {
-        readonly T result;
-        readonly IAwaiter<T> awaiter;
-
-        [DebuggerHidden]
-        public UniTask(T result)
-        {
-            this.result = result;
-            this.awaiter = null;
-        }
-
-        [DebuggerHidden]
-        public UniTask(IAwaiter<T> awaiter)
-        {
-            this.result = default(T);
-            this.awaiter = awaiter;
-        }
-
-        [DebuggerHidden]
-        public UniTask(Func<UniTask<T>> factory)
-        {
-            this.result = default(T);
-            this.awaiter = new LazyPromise<T>(factory);
-        }
-
-        [DebuggerHidden]
-        public AwaiterStatus Status
-        {
-            get
-            {
-                return awaiter == null ? AwaiterStatus.Succeeded : awaiter.Status;
-            }
-        }
-
-        [DebuggerHidden]
-        public bool IsCompleted
-        {
-            get
-            {
-                return awaiter == null ? true : awaiter.IsCompleted;
-            }
-        }
-
-        [DebuggerHidden]
-        public T Result
-        {
-            get
-            {
-                if (awaiter == null)
-                {
-                    return result;
-                }
-                else
-                {
-                    return awaiter.GetResult();
-                }
-            }
-        }
-
-        [DebuggerHidden]
-        public Awaiter GetAwaiter()
-        {
-            return new Awaiter(this);
-        }
-
-        /// <summary>
-        /// returns (bool IsCanceled, T Result) instead of throws OperationCanceledException.
-        /// </summary>
-        public UniTask<(bool IsCanceled, T Result)> SuppressCancellationThrow()
-        {
-            var status = Status;
-            if (status == AwaiterStatus.Succeeded)
-            {
-                return new UniTask<(bool, T)>((false, Result));
-            }
-            else if (status == AwaiterStatus.Canceled)
-            {
-                return new UniTask<(bool, T)>((true, default(T)));
-            }
-            return new UniTask<(bool, T)>(new IsCanceledAwaiter(awaiter));
-        }
-
-        public bool Equals(UniTask<T> other)
-        {
-            if (this.awaiter == null && other.awaiter == null)
-            {
-                return EqualityComparer<T>.Default.Equals(this.result, other.result);
-            }
-            else if (this.awaiter != null && other.awaiter != null)
-            {
-                return this.awaiter == other.awaiter;
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        public override int GetHashCode()
-        {
-            if (this.awaiter == null)
-            {
-                if (result == null) return 0;
-                return result.GetHashCode();
-            }
-            else
-            {
-                return this.awaiter.GetHashCode();
-            }
-        }
-
-        public override string ToString()
-        {
-            return (this.awaiter == null) ? result.ToString()
-                 : (this.awaiter.Status == AwaiterStatus.Succeeded) ? this.awaiter.GetResult().ToString()
-                 : "(" + this.awaiter.Status + ")";
-        }
-
-        public static implicit operator UniTask(UniTask<T> task)
-        {
-            if (task.awaiter != null)
-            {
-                return new UniTask(task.awaiter);
-            }
-            else
-            {
-                return new UniTask();
-            }
-        }
-
-        class IsCanceledAwaiter : IAwaiter<(bool, T)>
-        {
-            readonly IAwaiter<T> awaiter;
-
-            public IsCanceledAwaiter(IAwaiter<T> awaiter)
-            {
-                this.awaiter = awaiter;
-            }
-
-            public bool IsCompleted => awaiter.IsCompleted;
-
-            public AwaiterStatus Status => awaiter.Status;
-
-            public (bool, T) GetResult()
-            {
-                if (awaiter.Status == AwaiterStatus.Canceled)
-                {
-                    return (true, default(T));
-                }
-                return (false, awaiter.GetResult());
-            }
-
-            public void OnCompleted(Action continuation)
-            {
-                awaiter.OnCompleted(continuation);
-            }
-
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                awaiter.UnsafeOnCompleted(continuation);
-            }
-
-            void IAwaiter.GetResult()
-            {
-                awaiter.GetResult();
-            }
-        }
-
-        public struct Awaiter : IAwaiter<T>
-        {
-            readonly UniTask<T> task;
-
-            [DebuggerHidden]
-            public Awaiter(in UniTask<T> task)
-            {
-                this.task = task;
-            }
-
-            [DebuggerHidden]
-            public bool IsCompleted => task.IsCompleted;
-
-            [DebuggerHidden]
-            public AwaiterStatus Status => task.Status;
-
-            [DebuggerHidden]
-            void IAwaiter.GetResult() => GetResult();
-
-            [DebuggerHidden]
-            public T GetResult() => task.Result;
-
-            [DebuggerHidden]
-            public void OnCompleted(Action continuation)
-            {
-                if (task.awaiter != null)
-                {
-                    task.awaiter.OnCompleted(continuation);
-                }
-                else
-                {
-                    continuation();
-                }
-            }
-
-            [DebuggerHidden]
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                if (task.awaiter != null)
-                {
-                    task.awaiter.UnsafeOnCompleted(continuation);
-                }
-                else
-                {
-                    continuation();
-                }
-            }
-        }
-    }
 }
 
 #endif
diff --git a/Assets/UniRx.Async/UniTaskCompletionSource.cs b/Assets/UniRx.Async/UniTaskCompletionSource.cs
index 27355a4..73427f8 100644
--- a/Assets/UniRx.Async/UniTaskCompletionSource.cs
+++ b/Assets/UniRx.Async/UniTaskCompletionSource.cs
@@ -2,7 +2,6 @@
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using System.Runtime.ExceptionServices;
@@ -12,52 +11,24 @@ using UniRx.Async.Internal;
 
 namespace UniRx.Async
 {
-    // TODO: Remove all?
-
-    internal class ExceptionHolder
-    {
-        ExceptionDispatchInfo exception;
-        bool calledGet = false;
-
-        public ExceptionHolder(ExceptionDispatchInfo exception)
-        {
-            this.exception = exception;
-        }
-
-        public ExceptionDispatchInfo GetException()
-        {
-            if (!calledGet)
-            {
-                calledGet = true;
-                GC.SuppressFinalize(this);
-            }
-            return exception;
-        }
-
-        ~ExceptionHolder()
-        {
-            UniTaskScheduler.PublishUnobservedTaskException(exception.SourceException);
-        }
-    }
-
     public interface IResolvePromise
     {
-        bool TrySetResult();
+        void SetResult();
     }
 
     public interface IResolvePromise<T>
     {
-        bool TrySetResult(T value);
+        void SetResult(T value);
     }
 
     public interface IRejectPromise
     {
-        bool TrySetException(Exception exception);
+        void SetException(Exception exception);
     }
 
     public interface ICancelPromise
     {
-        bool TrySetCanceled();
+        void SetCanceled(CancellationToken cancellationToken = default);
     }
 
     public interface IPromise<T> : IResolvePromise<T>, IRejectPromise, ICancelPromise
@@ -68,350 +39,6 @@ namespace UniRx.Async
     {
     }
 
-    public class UniTaskCompletionSource : IAwaiter, IPromise
-    {
-        // State(= AwaiterStatus)
-        const int Pending = 0;
-        const int Succeeded = 1;
-        const int Faulted = 2;
-        const int Canceled = 3;
-
-        int state = 0;
-        bool handled = false;
-        ExceptionHolder exception;
-        object continuation; // action or list
-
-        AwaiterStatus IAwaiter.Status => (AwaiterStatus)state;
-
-        bool IAwaiter.IsCompleted => state != Pending;
-
-        public UniTask Task => new UniTask(this);
-
-        public UniTaskCompletionSource()
-        {
-            TaskTracker.TrackActiveTask(this, 2);
-        }
-
-        [Conditional("UNITY_EDITOR")]
-        internal void MarkHandled()
-        {
-            if (!handled)
-            {
-                handled = true;
-                TaskTracker.RemoveTracking(this);
-            }
-        }
-
-        void IAwaiter.GetResult()
-        {
-            MarkHandled();
-
-            if (state == Succeeded)
-            {
-                return;
-            }
-            else if (state == Faulted)
-            {
-                exception.GetException().Throw();
-            }
-            else if (state == Canceled)
-            {
-                if (exception != null)
-                {
-                    exception.GetException().Throw(); // guranteed operation canceled exception.
-                }
-
-                throw new OperationCanceledException();
-            }
-            else // Pending
-            {
-                throw new NotSupportedException("UniTask does not allow call GetResult directly when task not completed. Please use 'await'.");
-            }
-        }
-
-        void ICriticalNotifyCompletion.UnsafeOnCompleted(Action action)
-        {
-            if (Interlocked.CompareExchange(ref continuation, (object)action, null) == null)
-            {
-                if (state != Pending)
-                {
-                    TryInvokeContinuation();
-                }
-            }
-            else
-            {
-                var c = continuation;
-                if (c is Action)
-                {
-                    var list = new List<Action>();
-                    list.Add((Action)c);
-                    list.Add(action);
-                    if (Interlocked.CompareExchange(ref continuation, list, c) == c)
-                    {
-                        goto TRYINVOKE;
-                    }
-                }
-
-                var l = (List<Action>)continuation;
-                lock (l)
-                {
-                    l.Add(action);
-                }
-
-                TRYINVOKE:
-                if (state != Pending)
-                {
-                    TryInvokeContinuation();
-                }
-            }
-        }
-
-        void TryInvokeContinuation()
-        {
-            var c = Interlocked.Exchange(ref continuation, null);
-            if (c != null)
-            {
-                if (c is Action)
-                {
-                    ((Action)c).Invoke();
-                }
-                else
-                {
-                    var l = (List<Action>)c;
-                    var cnt = l.Count;
-                    for (int i = 0; i < cnt; i++)
-                    {
-                        l[i].Invoke();
-                    }
-                }
-            }
-        }
-
-        public bool TrySetResult()
-        {
-            if (Interlocked.CompareExchange(ref state, Succeeded, Pending) == Pending)
-            {
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        public bool TrySetException(Exception exception)
-        {
-            if (Interlocked.CompareExchange(ref state, Faulted, Pending) == Pending)
-            {
-                this.exception = new ExceptionHolder(ExceptionDispatchInfo.Capture(exception));
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        public bool TrySetCanceled()
-        {
-            if (Interlocked.CompareExchange(ref state, Canceled, Pending) == Pending)
-            {
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        public bool TrySetCanceled(OperationCanceledException exception)
-        {
-            if (Interlocked.CompareExchange(ref state, Canceled, Pending) == Pending)
-            {
-                this.exception = new ExceptionHolder(ExceptionDispatchInfo.Capture(exception));
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        void INotifyCompletion.OnCompleted(Action continuation)
-        {
-            ((ICriticalNotifyCompletion)this).UnsafeOnCompleted(continuation);
-        }
-    }
-
-    public class UniTaskCompletionSource<T> : IAwaiter<T>, IPromise<T>
-    {
-        // State(= AwaiterStatus)
-        const int Pending = 0;
-        const int Succeeded = 1;
-        const int Faulted = 2;
-        const int Canceled = 3;
-
-        int state = 0;
-        T value;
-        bool handled = false;
-        ExceptionHolder exception;
-        object continuation; // action or list
-
-        bool IAwaiter.IsCompleted => state != Pending;
-
-        public UniTask<T> Task => new UniTask<T>(this);
-        public UniTask UnitTask => new UniTask(this);
-
-        AwaiterStatus IAwaiter.Status => (AwaiterStatus)state;
-
-        public UniTaskCompletionSource()
-        {
-            TaskTracker.TrackActiveTask(this, 2);
-        }
-
-        [Conditional("UNITY_EDITOR")]
-        internal void MarkHandled()
-        {
-            if (!handled)
-            {
-                handled = true;
-                TaskTracker.RemoveTracking(this);
-            }
-        }
-
-        T IAwaiter<T>.GetResult()
-        {
-            MarkHandled();
-
-            if (state == Succeeded)
-            {
-                return value;
-            }
-            else if (state == Faulted)
-            {
-                exception.GetException().Throw();
-            }
-            else if (state == Canceled)
-            {
-                if (exception != null)
-                {
-                    exception.GetException().Throw(); // guranteed operation canceled exception.
-                }
-
-                throw new OperationCanceledException();
-            }
-            else // Pending
-            {
-                throw new NotSupportedException("UniTask does not allow call GetResult directly when task not completed. Please use 'await'.");
-            }
-
-            return default(T);
-        }
-
-        void ICriticalNotifyCompletion.UnsafeOnCompleted(Action action)
-        {
-            if (Interlocked.CompareExchange(ref continuation, (object)action, null) == null)
-            {
-                if (state != Pending)
-                {
-                    TryInvokeContinuation();
-                }
-            }
-            else
-            {
-                var c = continuation;
-                if (c is Action)
-                {
-                    var list = new List<Action>();
-                    list.Add((Action)c);
-                    list.Add(action);
-                    if (Interlocked.CompareExchange(ref continuation, list, c) == c)
-                    {
-                        goto TRYINVOKE;
-                    }
-                }
-
-                var l = (List<Action>)continuation;
-                lock (l)
-                {
-                    l.Add(action);
-                }
-
-                TRYINVOKE:
-                if (state != Pending)
-                {
-                    TryInvokeContinuation();
-                }
-            }
-        }
-
-        void TryInvokeContinuation()
-        {
-            var c = Interlocked.Exchange(ref continuation, null);
-            if (c != null)
-            {
-                if (c is Action)
-                {
-                    ((Action)c).Invoke();
-                }
-                else
-                {
-                    var l = (List<Action>)c;
-                    var cnt = l.Count;
-                    for (int i = 0; i < cnt; i++)
-                    {
-                        l[i].Invoke();
-                    }
-                }
-            }
-        }
-
-        public bool TrySetResult(T value)
-        {
-            if (Interlocked.CompareExchange(ref state, Succeeded, Pending) == Pending)
-            {
-                this.value = value;
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        public bool TrySetException(Exception exception)
-        {
-            if (Interlocked.CompareExchange(ref state, Faulted, Pending) == Pending)
-            {
-                this.exception = new ExceptionHolder(ExceptionDispatchInfo.Capture(exception));
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        public bool TrySetCanceled()
-        {
-            if (Interlocked.CompareExchange(ref state, Canceled, Pending) == Pending)
-            {
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        public bool TrySetCanceled(OperationCanceledException exception)
-        {
-            if (Interlocked.CompareExchange(ref state, Canceled, Pending) == Pending)
-            {
-                this.exception = new ExceptionHolder(ExceptionDispatchInfo.Capture(exception));
-                TryInvokeContinuation();
-                return true;
-            }
-            return false;
-        }
-
-        void IAwaiter.GetResult()
-        {
-            ((IAwaiter<T>)this).GetResult();
-        }
-
-        void INotifyCompletion.OnCompleted(Action continuation)
-        {
-            ((ICriticalNotifyCompletion)this).UnsafeOnCompleted(continuation);
-        }
-    }
-
     [StructLayout(LayoutKind.Auto)]
     public struct UniTaskCompletionSourceCore<TResult>
     {
@@ -602,12 +229,22 @@ namespace UniRx.Async
         }
     }
 
-    public class UniTaskCompletionSource2 : IUniTaskSource
+    internal static class UniTaskCompletionSourceCoreShared // separated out of generic to avoid unnecessary duplication
+    {
+        internal static readonly Action<object> s_sentinel = CompletionSentinel;
+
+        private static void CompletionSentinel(object _) // named method to aid debugging
+        {
+            throw new InvalidOperationException("The sentinel delegate should never be invoked.");
+        }
+    }
+
+    public class UniTaskCompletionSource : IUniTaskSource, IPromise
     {
         UniTaskCompletionSourceCore<AsyncUnit> core;
         bool handled = false;
 
-        public UniTaskCompletionSource2()
+        public UniTaskCompletionSource()
         {
             TaskTracker2.TrackActiveTask(this, 2);
         }
@@ -622,11 +259,11 @@ namespace UniRx.Async
             }
         }
 
-        public UniTask2 Task
+        public UniTask Task
         {
             get
             {
-                return new UniTask2(this, core.Version);
+                return new UniTask(this, core.Version);
             }
         }
 
@@ -674,14 +311,14 @@ namespace UniRx.Async
             core.OnCompleted(continuation, state, token);
         }
 
-        ~UniTaskCompletionSource2()
+        ~UniTaskCompletionSource()
         {
             // clear error information.
             core.Reset();
         }
     }
 
-    public class AutoResetUniTaskCompletionSource : IUniTaskSource, IPromisePoolItem
+    public class AutoResetUniTaskCompletionSource : IUniTaskSource, IPromisePoolItem, IPromise
     {
         static readonly PromisePool<AutoResetUniTaskCompletionSource> pool = new PromisePool<AutoResetUniTaskCompletionSource>();
 
@@ -722,11 +359,11 @@ namespace UniRx.Async
             return source;
         }
 
-        public UniTask2 Task
+        public UniTask Task
         {
             get
             {
-                return new UniTask2(this, core.Version);
+                return new UniTask(this, core.Version);
             }
         }
 
@@ -737,7 +374,7 @@ namespace UniRx.Async
 
         public void SetCanceled(CancellationToken cancellationToken = default)
         {
-            core.SetCancellation(cancellationToken);
+            core.SetCanceled(cancellationToken);
         }
 
         public void SetException(Exception exception)
@@ -789,12 +426,12 @@ namespace UniRx.Async
         }
     }
 
-    public class UniTaskCompletionSource2<T> : IUniTaskSource<T>
+    public class UniTaskCompletionSource<T> : IUniTaskSource<T>, IPromise<T>
     {
         UniTaskCompletionSourceCore<T> core;
         bool handled = false;
 
-        public UniTaskCompletionSource2()
+        public UniTaskCompletionSource()
         {
             TaskTracker2.TrackActiveTask(this, 2);
         }
@@ -809,11 +446,11 @@ namespace UniRx.Async
             }
         }
 
-        public UniTask2<T> Task
+        public UniTask<T> Task
         {
             get
             {
-                return new UniTask2<T>(this, core.Version);
+                return new UniTask<T>(this, core.Version);
             }
         }
 
@@ -831,7 +468,7 @@ namespace UniRx.Async
 
         public void SetCanceled(CancellationToken cancellationToken = default)
         {
-            core.SetCancellation(cancellationToken);
+            core.SetCanceled(cancellationToken);
         }
 
         public void SetException(Exception exception)
@@ -865,14 +502,14 @@ namespace UniRx.Async
             core.OnCompleted(continuation, state, token);
         }
 
-        ~UniTaskCompletionSource2()
+        ~UniTaskCompletionSource()
         {
             // clear error information.
             core.Reset();
         }
     }
 
-    public class AutoResetUniTaskCompletionSource<T> : IUniTaskSource<T>, IPromisePoolItem
+    public class AutoResetUniTaskCompletionSource<T> : IUniTaskSource<T>, IPromisePoolItem, IPromise<T>
     {
         static readonly PromisePool<AutoResetUniTaskCompletionSource<T>> pool = new PromisePool<AutoResetUniTaskCompletionSource<T>>();
 
@@ -892,7 +529,7 @@ namespace UniRx.Async
         public static AutoResetUniTaskCompletionSource<T> CreateFromCanceled(CancellationToken cancellationToken, out short token)
         {
             var source = Create();
-            source.SetCancellation(cancellationToken);
+            source.SetCanceled(cancellationToken);
             token = source.core.Version;
             return source;
         }
@@ -913,11 +550,11 @@ namespace UniRx.Async
             return source;
         }
 
-        public UniTask2<T> Task
+        public UniTask<T> Task
         {
             get
             {
-                return new UniTask2<T>(this, core.Version);
+                return new UniTask<T>(this, core.Version);
             }
         }
 
@@ -928,7 +565,7 @@ namespace UniRx.Async
 
         public void SetCanceled(CancellationToken cancellationToken = default)
         {
-            core.SetCancellation(cancellationToken);
+            core.SetCanceled(cancellationToken);
         }
 
         public void SetException(Exception exception)
@@ -983,16 +620,6 @@ namespace UniRx.Async
             }
         }
     }
-
-    internal static class UniTaskCompletionSourceCoreShared // separated out of generic to avoid unnecessary duplication
-    {
-        internal static readonly Action<object> s_sentinel = CompletionSentinel;
-
-        private static void CompletionSentinel(object _) // named method to aid debugging
-        {
-            throw new InvalidOperationException("The sentinel delegate should never be invoked.");
-        }
-    }
 }
 
 #endif
\ No newline at end of file
diff --git a/Assets/UniRx.Async/UniTaskExtensions.cs b/Assets/UniRx.Async/UniTaskExtensions.cs
index 6cdfaf8..64c0f9b 100644
--- a/Assets/UniRx.Async/UniTaskExtensions.cs
+++ b/Assets/UniRx.Async/UniTaskExtensions.cs
@@ -10,12 +10,12 @@ using UniRx.Async.Internal;
 
 namespace UniRx.Async
 {
-    public static partial class UniTaskExtensions2
+    public static partial class UniTaskExtensions
     {
         /// <summary>
         /// Convert UniTask -> UniTask[AsyncUnit].
         /// </summary>
-        public static UniTask2<AsyncUnit> AsAsyncUnitUniTask(this UniTask2 task)
+        public static UniTask<AsyncUnit> AsAsyncUnitUniTask(this UniTask task)
         {
             // use implicit conversion
             return task;
@@ -24,7 +24,7 @@ namespace UniRx.Async
         /// <summary>
         /// Convert UniTask[T] -> UniTask.
         /// </summary>
-        public static UniTask2 AsUniTask<T>(this UniTask2<T> task)
+        public static UniTask AsUniTask<T>(this UniTask<T> task)
         {
             // use implicit conversion
             return task;
@@ -33,13 +33,13 @@ namespace UniRx.Async
         /// <summary>
         /// Convert Task[T] -> UniTask[T].
         /// </summary>
-        public static UniTask2<T> AsUniTask<T>(this Task<T> task, bool useCurrentSynchronizationContext = true)
+        public static UniTask<T> AsUniTask<T>(this Task<T> task, bool useCurrentSynchronizationContext = true)
         {
-            var promise = new UniTaskCompletionSource2<T>();
+            var promise = new UniTaskCompletionSource<T>();
 
             task.ContinueWith((x, state) =>
             {
-                var p = (UniTaskCompletionSource2<T>)state;
+                var p = (UniTaskCompletionSource<T>)state;
 
                 switch (x.Status)
                 {
@@ -63,13 +63,13 @@ namespace UniRx.Async
         /// <summary>
         /// Convert Task -> UniTask.
         /// </summary>
-        public static UniTask2 AsUniTask(this Task task, bool useCurrentSynchronizationContext = true)
+        public static UniTask AsUniTask(this Task task, bool useCurrentSynchronizationContext = true)
         {
-            var promise = new UniTaskCompletionSource2();
+            var promise = new UniTaskCompletionSource();
 
             task.ContinueWith((x, state) =>
             {
-                var p = (UniTaskCompletionSource2)state;
+                var p = (UniTaskCompletionSource)state;
 
                 switch (x.Status)
                 {
@@ -90,7 +90,7 @@ namespace UniRx.Async
             return promise.Task;
         }
 
-        public static Task<T> AsTask<T>(this UniTask2<T> task)
+        public static Task<T> AsTask<T>(this UniTask<T> task)
         {
             try
             {
@@ -112,7 +112,7 @@ namespace UniRx.Async
 
                 awaiter.SourceOnCompleted(state =>
                 {
-                    var (inTcs, inAwaiter) = ((TaskCompletionSource<T>, UniTask2<T>.Awaiter))state;
+                    var (inTcs, inAwaiter) = ((TaskCompletionSource<T>, UniTask<T>.Awaiter))state;
                     try
                     {
                         var result = inAwaiter.GetResult();
@@ -132,7 +132,7 @@ namespace UniRx.Async
             }
         }
 
-        public static Task AsTask(this UniTask2 task)
+        public static Task AsTask(this UniTask task)
         {
             try
             {
@@ -154,7 +154,7 @@ namespace UniRx.Async
 
                 awaiter.SourceOnCompleted(state =>
                 {
-                    var (inTcs, inAwaiter) = ((TaskCompletionSource<object>, UniTask2.Awaiter))state;
+                    var (inTcs, inAwaiter) = ((TaskCompletionSource<object>, UniTask.Awaiter))state;
                     try
                     {
                         inAwaiter.GetResult();
@@ -174,481 +174,6 @@ namespace UniRx.Async
             }
         }
 
-        public static IEnumerator ToCoroutine<T>(this UniTask2<T> task, Action<T> resultHandler = null, Action<Exception> exceptionHandler = null)
-        {
-            return new ToCoroutineEnumerator<T>(task, resultHandler, exceptionHandler);
-        }
-
-        public static IEnumerator ToCoroutine(this UniTask2 task, Action<Exception> exceptionHandler = null)
-        {
-            return new ToCoroutineEnumerator(task, exceptionHandler);
-        }
-
-        public static UniTask Timeout(this UniTask2 task, TimeSpan timeout, bool ignoreTimeScale = true, PlayerLoopTiming timeoutCheckTiming = PlayerLoopTiming.Update, CancellationTokenSource taskCancellationTokenSource = null)
-        {
-            return Timeout(task.AsAsyncUnitUniTask(), timeout, ignoreTimeScale, timeoutCheckTiming, taskCancellationTokenSource);
-        }
-
-        // TODO: require UniTask2.Delay, WhenAny, etc...
-
-        public static async UniTask<T> Timeout<T>(this UniTask2<T> task, TimeSpan timeout, bool ignoreTimeScale = true, PlayerLoopTiming timeoutCheckTiming = PlayerLoopTiming.Update, CancellationTokenSource taskCancellationTokenSource = null)
-        {
-            // left, right both suppress operation canceled exception.
-
-            var delayCancellationTokenSource = new CancellationTokenSource();
-            var timeoutTask = (UniTask)UniTask.Delay(timeout, ignoreTimeScale, timeoutCheckTiming).SuppressCancellationThrow();
-
-            var (hasValue, value) = await UniTask.WhenAny(task.SuppressCancellationThrow(), timeoutTask);
-
-            if (!hasValue)
-            {
-                if (taskCancellationTokenSource != null)
-                {
-                    taskCancellationTokenSource.Cancel();
-                    taskCancellationTokenSource.Dispose();
-                }
-
-                throw new TimeoutException("Exceed Timeout:" + timeout);
-            }
-            else
-            {
-                delayCancellationTokenSource.Cancel();
-                delayCancellationTokenSource.Dispose();
-            }
-
-            if (value.IsCanceled)
-            {
-                Error.ThrowOperationCanceledException();
-            }
-
-            return value.Result;
-        }
-
-        /// <summary>
-        /// Timeout with suppress OperationCanceledException. Returns (bool, IsCacneled).
-        /// </summary>
-        public static async UniTask2<bool> TimeoutWithoutException(this UniTask2 task, TimeSpan timeout, bool ignoreTimeScale = true, PlayerLoopTiming timeoutCheckTiming = PlayerLoopTiming.Update, CancellationTokenSource taskCancellationTokenSource = null)
-        {
-            var v = await TimeoutWithoutException(task.AsAsyncUnitUniTask(), timeout, ignoreTimeScale, timeoutCheckTiming, taskCancellationTokenSource);
-            return v.IsTimeout;
-        }
-
-
-        /// <summary>
-        /// Timeout with suppress OperationCanceledException. Returns (bool IsTimeout, T Result).
-        /// </summary>
-        public static async UniTask2<(bool IsTimeout, T Result)> TimeoutWithoutException<T>(this UniTask2<T> task, TimeSpan timeout, bool ignoreTimeScale = true, PlayerLoopTiming timeoutCheckTiming = PlayerLoopTiming.Update, CancellationTokenSource taskCancellationTokenSource = null)
-        {
-            // left, right both suppress operation canceled exception.
-
-            var delayCancellationTokenSource = new CancellationTokenSource();
-            var timeoutTask = (UniTask)UniTask.Delay(timeout, ignoreTimeScale, timeoutCheckTiming).SuppressCancellationThrow();
-
-            var (hasValue, value) = await UniTask.WhenAny(task.SuppressCancellationThrow(), timeoutTask);
-
-            if (!hasValue)
-            {
-                if (taskCancellationTokenSource != null)
-                {
-                    taskCancellationTokenSource.Cancel();
-                    taskCancellationTokenSource.Dispose();
-                }
-
-                return (true, default(T));
-            }
-            else
-            {
-                delayCancellationTokenSource.Cancel();
-                delayCancellationTokenSource.Dispose();
-            }
-
-            if (value.IsCanceled)
-            {
-                Error.ThrowOperationCanceledException();
-            }
-
-            return (false, value.Result);
-        }
-
-        public static void Forget(this UniTask2 task)
-        {
-            ForgetCore(task).Forget();
-        }
-
-        public static void Forget(this UniTask2 task, Action<Exception> exceptionHandler, bool handleExceptionOnMainThread = true)
-        {
-            if (exceptionHandler == null)
-            {
-                ForgetCore(task).Forget();
-            }
-            else
-            {
-                ForgetCoreWithCatch(task, exceptionHandler, handleExceptionOnMainThread).Forget();
-            }
-        }
-
-        // UniTask to UniTaskVoid
-        static async UniTaskVoid ForgetCore(UniTask2 task)
-        {
-            await task;
-        }
-
-        static async UniTaskVoid ForgetCoreWithCatch(UniTask2 task, Action<Exception> exceptionHandler, bool handleExceptionOnMainThread)
-        {
-            try
-            {
-                await task;
-            }
-            catch (Exception ex)
-            {
-                try
-                {
-                    if (handleExceptionOnMainThread)
-                    {
-                        await UniTask2.SwitchToMainThread();
-                    }
-                    exceptionHandler(ex);
-                }
-                catch (Exception ex2)
-                {
-                    UniTaskScheduler.PublishUnobservedTaskException(ex2);
-                }
-            }
-        }
-
-        public static void Forget<T>(this UniTask2<T> task)
-        {
-            ForgetCore(task).Forget();
-        }
-
-        public static void Forget<T>(this UniTask2<T> task, Action<Exception> exceptionHandler, bool handleExceptionOnMainThread = true)
-        {
-            if (exceptionHandler == null)
-            {
-                ForgetCore(task).Forget();
-            }
-            else
-            {
-                ForgetCoreWithCatch(task, exceptionHandler, handleExceptionOnMainThread).Forget();
-            }
-        }
-
-        // UniTask to UniTaskVoid
-        static async UniTaskVoid ForgetCore<T>(UniTask2<T> task)
-        {
-            await task;
-        }
-
-        static async UniTaskVoid ForgetCoreWithCatch<T>(UniTask2<T> task, Action<Exception> exceptionHandler, bool handleExceptionOnMainThread)
-        {
-            try
-            {
-                await task;
-            }
-            catch (Exception ex)
-            {
-                try
-                {
-                    if (handleExceptionOnMainThread)
-                    {
-                        await UniTask.SwitchToMainThread();
-                    }
-                    exceptionHandler(ex);
-                }
-                catch (Exception ex2)
-                {
-                    UniTaskScheduler.PublishUnobservedTaskException(ex2);
-                }
-            }
-        }
-
-        public static async UniTask2 ContinueWith<T>(this UniTask2<T> task, Action<T> continuationFunction)
-        {
-            continuationFunction(await task);
-        }
-
-        public static async UniTask2 ContinueWith<T>(this UniTask2<T> task, Func<T, UniTask2> continuationFunction)
-        {
-            await continuationFunction(await task);
-        }
-
-        public static async UniTask2<TR> ContinueWith<T, TR>(this UniTask2<T> task, Func<T, TR> continuationFunction)
-        {
-            return continuationFunction(await task);
-        }
-
-        public static async UniTask2<TR> ContinueWith<T, TR>(this UniTask2<T> task, Func<T, UniTask2<TR>> continuationFunction)
-        {
-            return await continuationFunction(await task);
-        }
-
-        public static async UniTask2 ContinueWith(this UniTask2 task, Action continuationFunction)
-        {
-            await task;
-            continuationFunction();
-        }
-
-        public static async UniTask2 ContinueWith(this UniTask2 task, Func<UniTask2> continuationFunction)
-        {
-            await task;
-            await continuationFunction();
-        }
-
-        public static async UniTask2<T> ContinueWith<T>(this UniTask2 task, Func<T> continuationFunction)
-        {
-            await task;
-            return continuationFunction();
-        }
-
-        public static async UniTask2<T> ContinueWith<T>(this UniTask2 task, Func<UniTask2<T>> continuationFunction)
-        {
-            await task;
-            return await continuationFunction();
-        }
-
-        public static async UniTask2 ConfigureAwait(this Task task, PlayerLoopTiming timing)
-        {
-            await task.ConfigureAwait(false);
-            await UniTask2.Yield(timing);
-        }
-
-        public static async UniTask2<T> ConfigureAwait<T>(this Task<T> task, PlayerLoopTiming timing)
-        {
-            var v = await task.ConfigureAwait(false);
-            await UniTask2.Yield(timing);
-            return v;
-        }
-
-        public static async UniTask2 ConfigureAwait(this UniTask2 task, PlayerLoopTiming timing)
-        {
-            await task;
-            await UniTask2.Yield(timing);
-        }
-
-        public static async UniTask2<T> ConfigureAwait<T>(this UniTask2<T> task, PlayerLoopTiming timing)
-        {
-            var v = await task;
-            await UniTask2.Yield(timing);
-            return v;
-        }
-
-        public static async UniTask2<T> Unwrap<T>(this UniTask2<UniTask2<T>> task)
-        {
-            return await await task;
-        }
-
-        public static async UniTask2 Unwrap<T>(this UniTask2<UniTask2> task)
-        {
-            await await task;
-        }
-
-        class ToCoroutineEnumerator : IEnumerator
-        {
-            bool completed;
-            UniTask2 task;
-            Action<Exception> exceptionHandler = null;
-            bool isStarted = false;
-            ExceptionDispatchInfo exception;
-
-            public ToCoroutineEnumerator(UniTask2 task, Action<Exception> exceptionHandler)
-            {
-                completed = false;
-                this.exceptionHandler = exceptionHandler;
-                this.task = task;
-            }
-
-            async UniTaskVoid RunTask(UniTask2 task)
-            {
-                try
-                {
-                    await task;
-                }
-                catch (Exception ex)
-                {
-                    if (exceptionHandler != null)
-                    {
-                        exceptionHandler(ex);
-                    }
-                    else
-                    {
-                        this.exception = ExceptionDispatchInfo.Capture(ex);
-                    }
-                }
-                finally
-                {
-                    completed = true;
-                }
-            }
-
-            public object Current => null;
-
-            public bool MoveNext()
-            {
-                if (!isStarted)
-                {
-                    isStarted = true;
-                    RunTask(task).Forget();
-                }
-
-                if (exception != null)
-                {
-                    // throw exception on iterator (main)thread.
-                    // unfortunately unity test-runner can not handle throw exception on hand-write IEnumerator.MoveNext.
-                    UnityEngine.Debug.LogException(exception.SourceException);
-                }
-
-                return !completed;
-            }
-
-            public void Reset()
-            {
-            }
-        }
-
-        class ToCoroutineEnumerator<T> : IEnumerator
-        {
-            bool completed;
-            Action<T> resultHandler = null;
-            Action<Exception> exceptionHandler = null;
-            bool isStarted = false;
-            UniTask2<T> task;
-            object current = null;
-            ExceptionDispatchInfo exception;
-
-            public ToCoroutineEnumerator(UniTask2<T> task, Action<T> resultHandler, Action<Exception> exceptionHandler)
-            {
-                completed = false;
-                this.task = task;
-                this.resultHandler = resultHandler;
-                this.exceptionHandler = exceptionHandler;
-            }
-
-            async UniTaskVoid RunTask(UniTask2<T> task)
-            {
-                try
-                {
-                    var value = await task;
-                    current = value; // boxed if T is struct...
-                    if (resultHandler != null)
-                    {
-                        resultHandler(value);
-                    }
-                }
-                catch (Exception ex)
-                {
-                    if (exceptionHandler != null)
-                    {
-                        exceptionHandler(ex);
-                    }
-                    else
-                    {
-                        this.exception = ExceptionDispatchInfo.Capture(ex);
-                    }
-                }
-                finally
-                {
-                    completed = true;
-                }
-            }
-
-            public object Current => current;
-
-            public bool MoveNext()
-            {
-                if (!isStarted)
-                {
-                    isStarted = true;
-                    RunTask(task).Forget();
-                }
-
-                if (exception != null)
-                {
-                    // throw exception on iterator (main)thread.
-                    // unfortunately unity test-runner can not handle throw exception on hand-write IEnumerator.MoveNext.
-                    UnityEngine.Debug.LogException(exception.SourceException);
-                }
-
-                return !completed;
-            }
-
-            public void Reset()
-            {
-            }
-        }
-    }
-
-    // TODO:remove
-    public static partial class UniTaskExtensions
-    {
-        /// <summary>
-        /// Convert UniTask -> UniTask[AsyncUnit].
-        /// </summary>
-        public static UniTask<AsyncUnit> AsAsyncUnitUniTask(this UniTask task)
-        {
-            // use implicit conversion
-            return task;
-        }
-
-        /// <summary>
-        /// Convert Task[T] -> UniTask[T].
-        /// </summary>
-        public static UniTask<T> AsUniTask<T>(this Task<T> task, bool useCurrentSynchronizationContext = true)
-        {
-            var promise = new UniTaskCompletionSource<T>();
-
-            task.ContinueWith((x, state) =>
-            {
-                var p = (UniTaskCompletionSource<T>)state;
-
-                switch (x.Status)
-                {
-                    case TaskStatus.Canceled:
-                        p.TrySetCanceled();
-                        break;
-                    case TaskStatus.Faulted:
-                        p.TrySetException(x.Exception);
-                        break;
-                    case TaskStatus.RanToCompletion:
-                        p.TrySetResult(x.Result);
-                        break;
-                    default:
-                        throw new NotSupportedException();
-                }
-            }, promise, useCurrentSynchronizationContext ? TaskScheduler.FromCurrentSynchronizationContext() : TaskScheduler.Current);
-
-            return new UniTask<T>(promise);
-        }
-
-        /// <summary>
-        /// Convert Task -> UniTask.
-        /// </summary>
-        public static UniTask AsUniTask(this Task task, bool useCurrentSynchronizationContext = true)
-        {
-            var promise = new UniTaskCompletionSource<AsyncUnit>();
-
-            task.ContinueWith((x, state) =>
-            {
-                var p = (UniTaskCompletionSource<AsyncUnit>)state;
-
-                switch (x.Status)
-                {
-                    case TaskStatus.Canceled:
-                        p.TrySetCanceled();
-                        break;
-                    case TaskStatus.Faulted:
-                        p.TrySetException(x.Exception);
-                        break;
-                    case TaskStatus.RanToCompletion:
-                        p.TrySetResult(default(AsyncUnit));
-                        break;
-                    default:
-                        throw new NotSupportedException();
-                }
-            }, promise, useCurrentSynchronizationContext ? TaskScheduler.FromCurrentSynchronizationContext() : TaskScheduler.Current);
-
-            return new UniTask(promise);
-        }
-
         public static IEnumerator ToCoroutine<T>(this UniTask<T> task, Action<T> resultHandler = null, Action<Exception> exceptionHandler = null)
         {
             return new ToCoroutineEnumerator<T>(task, resultHandler, exceptionHandler);
@@ -664,6 +189,8 @@ namespace UniRx.Async
             return Timeout(task.AsAsyncUnitUniTask(), timeout, ignoreTimeScale, timeoutCheckTiming, taskCancellationTokenSource);
         }
 
+        // TODO: require UniTask2.Delay, WhenAny, etc...
+
         public static async UniTask<T> Timeout<T>(this UniTask<T> task, TimeSpan timeout, bool ignoreTimeScale = true, PlayerLoopTiming timeoutCheckTiming = PlayerLoopTiming.Update, CancellationTokenSource taskCancellationTokenSource = null)
         {
             // left, right both suppress operation canceled exception.
@@ -1001,7 +528,7 @@ namespace UniRx.Async
                 try
                 {
                     var value = await task;
-                    current = value;
+                    current = value; // boxed if T is struct...
                     if (resultHandler != null)
                     {
                         resultHandler(value);