diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJoint.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJoint.cs
deleted file mode 100644
index c7d79a95d..000000000
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJoint.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-using System;
-using UnityEngine;
-
-namespace UniGLTF.SpringBoneJobs.Blittables
-{
-    /// <summary>
-    /// SpringBoneの各関節を表すデータ型
-    /// </summary>
-    [Serializable]
-    public struct BlittableJoint
-    {
-        public float stiffnessForce;
-        public float gravityPower;
-        public Vector3 gravityDir;
-        public float dragForce;
-        public float radius;
-    }
-}
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableLogic.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointImmutable.cs
similarity index 55%
rename from Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableLogic.cs
rename to Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointImmutable.cs
index 547ca4cbe..c185dbf43 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableLogic.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointImmutable.cs
@@ -4,16 +4,17 @@ using UnityEngine;
 namespace UniGLTF.SpringBoneJobs.Blittables
 {
     /// <summary>
-    /// SpringBoneの各関節に紐付いた計算情報を表すデータ型
+    /// Reconstruct に対して Immutable。
+    /// Jointの増減、初期姿勢の変更など構成の変更は Reconstruct が必要。
+    /// 変わりにくいスコープ。
     /// </summary>
     [Serializable]
-    public struct BlittableLogic
+    public struct BlittableJointImmutable
     {
         public int parentTransformIndex;
         public int headTransformIndex;
+        public int tailTransformIndex;
         public float length;
-        public Vector3 currentTail;
-        public Vector3 prevTail;
         public Quaternion localRotation;
         public Vector3 boneAxis;
     }
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableLogic.cs.meta b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointImmutable.cs.meta
similarity index 100%
rename from Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableLogic.cs.meta
rename to Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointImmutable.cs.meta
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointMutable.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointMutable.cs
new file mode 100644
index 000000000..bbbd8c3ac
--- /dev/null
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointMutable.cs
@@ -0,0 +1,21 @@
+using System;
+using UnityEngine;
+
+namespace UniGLTF.SpringBoneJobs.Blittables
+{
+    /// <summary>
+    /// Reconstruct に対して Mutable。
+    /// Reconstruct より軽量な JointReconfigure(仮) で変更できるようにする予定。
+    /// おもに Editor play で設定を変更しながら動作を見る用途を想定している。
+    /// JointReconfigure を呼ばなければ以前と同じで不変となる。
+    /// </summary>
+    [Serializable]
+    public struct BlittableJointMutable
+    {
+        public float stiffnessForce;
+        public float gravityPower;
+        public Vector3 gravityDir;
+        public float dragForce;
+        public float radius;
+    }
+}
\ No newline at end of file
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJoint.cs.meta b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointMutable.cs.meta
similarity index 100%
rename from Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJoint.cs.meta
rename to Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableJointMutable.cs.meta
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneBufferCombiner.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneBufferCombiner.cs
index 82d400e8a..6e9f77614 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneBufferCombiner.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneBufferCombiner.cs
@@ -19,11 +19,19 @@ namespace UniGLTF.SpringBoneJobs
     /// </summary>
     public sealed class FastSpringBoneBufferCombiner : IDisposable
     {
+        // 長さと index 同じ
+        private NativeArray<BlittableJointImmutable> _logics;
+        private NativeArray<BlittableJointMutable> _joints;
+
+        private NativeArray<Vector3> _prevTails;
+        private NativeArray<Vector3> _currentTails;
+        private NativeArray<Vector3> _nextTails;
+
         private NativeArray<BlittableSpring> _springs;
-        private NativeArray<BlittableTransform> _transforms;
+
         private NativeArray<BlittableCollider> _colliders;
-        private NativeArray<BlittableJoint> _joints;
-        private NativeArray<BlittableLogic> _logics;
+
+        private NativeArray<BlittableTransform> _transforms;
         private TransformAccessArray _transformAccessArray;
 
         private readonly LinkedList<FastSpringBoneBuffer> _buffers = new LinkedList<FastSpringBoneBuffer>();
@@ -32,15 +40,29 @@ namespace UniGLTF.SpringBoneJobs
 
         private bool _isDirty;
 
+        public NativeArray<BlittableJointImmutable> Logics => _logics;
+        public NativeArray<BlittableJointMutable> Joints => _joints;
+        public NativeArray<Vector3> PrevTails => _prevTails;
+        public NativeArray<Vector3> CurrentTails => _currentTails;
+        public NativeArray<Vector3> NextTails => _nextTails;
+
         public NativeArray<BlittableSpring> Springs => _springs;
-        public NativeArray<BlittableJoint> Joints => _joints;
+
+        public NativeArray<BlittableCollider> Colliders => _colliders;
+
         public NativeArray<BlittableTransform> Transforms => _transforms;
         public TransformAccessArray TransformAccessArray => _transformAccessArray;
-        public NativeArray<BlittableCollider> Colliders => _colliders;
-        public NativeArray<BlittableLogic> Logics => _logics;
 
         public bool HasBuffer => _batchedBuffers != null && _batchedBuffers.Length > 0;
 
+        public void FlipBuffer()
+        {
+            var tmp = _prevTails;
+            _prevTails = _currentTails;
+            _currentTails = _nextTails;
+            _nextTails = tmp;
+        }
+
         public void Register(FastSpringBoneBuffer buffer)
         {
             _buffers.AddLast(buffer);
@@ -82,7 +104,7 @@ namespace UniGLTF.SpringBoneJobs
                 var length = _batchedBufferLogicSizes[i];
                 if (!_batchedBuffers[i].IsDisposed && length > 0)
                 {
-                    NativeArray<BlittableLogic>.Copy(_logics, logicsIndex, _batchedBuffers[i].Logics, 0, length);
+                    NativeArray<BlittableJointImmutable>.Copy(_logics, logicsIndex, _batchedBuffers[i].Logics, 0, length);
                 }
 
                 logicsIndex += length;
@@ -123,26 +145,29 @@ namespace UniGLTF.SpringBoneJobs
                 logicsCount += buffer.Logics.Length;
                 transformsCount += buffer.BlittableTransforms.Length;
             }
-
             Profiler.EndSample();
 
             // バッファの構築
             Profiler.BeginSample("FastSpringBone.ReconstructBuffers.CreateBuffers");
+
+            _logics = new NativeArray<BlittableJointImmutable>(logicsCount, Allocator.Persistent);
+            _joints = new NativeArray<BlittableJointMutable>(logicsCount, Allocator.Persistent);
+            _prevTails = new NativeArray<Vector3>(logicsCount, Allocator.Persistent);
+            _currentTails = new NativeArray<Vector3>(logicsCount, Allocator.Persistent);
+            _nextTails = new NativeArray<Vector3>(logicsCount, Allocator.Persistent);
+
             _springs = new NativeArray<BlittableSpring>(springsCount, Allocator.Persistent);
 
-            _joints = new NativeArray<BlittableJoint>(logicsCount, Allocator.Persistent);
-            _logics = new NativeArray<BlittableLogic>(logicsCount, Allocator.Persistent);
             _colliders = new NativeArray<BlittableCollider>(collidersCount, Allocator.Persistent);
 
             _transforms = new NativeArray<BlittableTransform>(transformsCount, Allocator.Persistent);
             Profiler.EndSample();
 
+            Profiler.BeginSample("FastSpringBone.ReconstructBuffers.ScheduleLoadBufferJobs");
             var springsOffset = 0;
             var collidersOffset = 0;
             var logicsOffset = 0;
             var transformOffset = 0;
-
-            Profiler.BeginSample("FastSpringBone.ReconstructBuffers.ScheduleLoadBufferJobs");
             for (var i = 0; i < _batchedBuffers.Length; i++)
             {
                 var buffer = _batchedBuffers[i];
@@ -151,10 +176,10 @@ namespace UniGLTF.SpringBoneJobs
                 handle = new LoadTransformsJob
                 {
                     SrcTransforms = buffer.BlittableTransforms,
-                    DestTransforms =
-                        new NativeSlice<BlittableTransform>(_transforms, transformOffset,
+                    DestTransforms = new NativeSlice<BlittableTransform>(_transforms, transformOffset,
                             buffer.BlittableTransforms.Length)
                 }.Schedule(buffer.BlittableTransforms.Length, 1, handle);
+
                 handle = new LoadSpringsJob
                 {
                     SrcSprings = buffer.Springs,
@@ -163,18 +188,20 @@ namespace UniGLTF.SpringBoneJobs
                     LogicsOffset = logicsOffset,
                     TransformOffset = transformOffset,
                 }.Schedule(buffer.Springs.Length, 1, handle);
+
                 handle = new LoadCollidersJob
                 {
                     SrcColliders = buffer.Colliders,
-                    DestColliders =
-                        new NativeSlice<BlittableCollider>(_colliders, collidersOffset, buffer.Colliders.Length)
+                    DestColliders = new NativeSlice<BlittableCollider>(_colliders, collidersOffset, buffer.Colliders.Length)
                 }.Schedule(buffer.Colliders.Length, 1, handle);
+
                 handle = new OffsetLogicsJob
                 {
                     SrcLogics = buffer.Logics,
                     SrcJoints = buffer.Joints,
-                    DestLogics = new NativeSlice<BlittableLogic>(_logics, logicsOffset, buffer.Logics.Length),
-                    DestJoints = new NativeSlice<BlittableJoint>(_joints, logicsOffset, buffer.Logics.Length),
+
+                    DestLogics = new NativeSlice<BlittableJointImmutable>(_logics, logicsOffset, buffer.Logics.Length),
+                    DestJoints = new NativeSlice<BlittableJointMutable>(_joints, logicsOffset, buffer.Logics.Length),
                 }.Schedule(buffer.Logics.Length, 1, handle);
 
                 springsOffset += buffer.Springs.Length;
@@ -183,6 +210,8 @@ namespace UniGLTF.SpringBoneJobs
                 transformOffset += buffer.BlittableTransforms.Length;
             }
 
+            handle = InitCurrentTails(handle);
+
             // TransformAccessArrayの構築と並行してJobを行うため、この時点で走らせておく
             JobHandle.ScheduleBatchedJobs();
             Profiler.EndSample();
@@ -205,14 +234,35 @@ namespace UniGLTF.SpringBoneJobs
             return handle;
         }
 
+        /// <summary>
+        /// Transform から currentTail を更新。
+        /// prevTail も同じ内容にする(速度0)。
+        /// </summary>
+        /// <param name="handle"></param>
+        /// <returns></returns>
+        public JobHandle InitCurrentTails(JobHandle handle)
+        {
+            return new InitCurrentTailsJob
+            {
+                Logics = Logics,
+                Transforms = Transforms,
+                CurrentTails = CurrentTails,
+                PrevTails = PrevTails,
+                NextTails = NextTails,
+            }.Schedule(Logics.Length, 1, handle);
+        }
+
         private void DisposeAllBuffers()
         {
-            if (_springs.IsCreated) _springs.Dispose();
+            if (_logics.IsCreated) _logics.Dispose();
             if (_joints.IsCreated) _joints.Dispose();
+            if (_prevTails.IsCreated) _prevTails.Dispose();
+            if (_currentTails.IsCreated) _currentTails.Dispose();
+            if (_nextTails.IsCreated) _nextTails.Dispose();
+            if (_springs.IsCreated) _springs.Dispose();
+            if (_colliders.IsCreated) _colliders.Dispose();
             if (_transforms.IsCreated) _transforms.Dispose();
             if (_transformAccessArray.isCreated) _transformAccessArray.Dispose();
-            if (_colliders.IsCreated) _colliders.Dispose();
-            if (_logics.IsCreated) _logics.Dispose();
         }
 
         public void Dispose()
@@ -275,10 +325,10 @@ namespace UniGLTF.SpringBoneJobs
 #endif
         private struct OffsetLogicsJob : IJobParallelFor
         {
-            [ReadOnly] public NativeSlice<BlittableLogic> SrcLogics;
-            [ReadOnly] public NativeSlice<BlittableJoint> SrcJoints;
-            [WriteOnly] public NativeSlice<BlittableLogic> DestLogics;
-            [WriteOnly] public NativeSlice<BlittableJoint> DestJoints;
+            [ReadOnly] public NativeSlice<BlittableJointImmutable> SrcLogics;
+            [ReadOnly] public NativeSlice<BlittableJointMutable> SrcJoints;
+            [WriteOnly] public NativeSlice<BlittableJointImmutable> DestLogics;
+            [WriteOnly] public NativeSlice<BlittableJointMutable> DestJoints;
 
             public void Execute(int index)
             {
@@ -286,5 +336,37 @@ namespace UniGLTF.SpringBoneJobs
                 DestJoints[index] = SrcJoints[index];
             }
         }
+
+#if ENABLE_SPRINGBONE_BURST
+        [BurstCompile]
+#endif
+        private struct InitCurrentTailsJob : IJobParallelFor
+        {
+            [ReadOnly] public NativeArray<BlittableJointImmutable> Logics;
+            [ReadOnly] public NativeArray<BlittableTransform> Transforms;
+            [WriteOnly] public NativeSlice<Vector3> CurrentTails;
+            [WriteOnly] public NativeSlice<Vector3> PrevTails;
+            [WriteOnly] public NativeSlice<Vector3> NextTails;
+
+            public void Execute(int jointIndex)
+            {
+                var tailIndex = Logics[jointIndex].tailTransformIndex;
+                if (tailIndex == -1)
+                {
+                    // tail 無い
+                    var tail = Transforms[Logics[jointIndex].headTransformIndex];
+                    CurrentTails[jointIndex] = tail.position;
+                    PrevTails[jointIndex] = tail.position;
+                    NextTails[jointIndex] = tail.position;
+                }
+                else
+                {
+                    var tail = Transforms[tailIndex];
+                    CurrentTails[jointIndex] = tail.position;
+                    PrevTails[jointIndex] = tail.position;
+                    NextTails[jointIndex] = tail.position;
+                }
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneScheduler.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneScheduler.cs
index cbdc158b8..b35e7ec99 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneScheduler.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/FastSpringBoneScheduler.cs
@@ -31,12 +31,17 @@ namespace UniGLTF.SpringBoneJobs
                 Transforms = _bufferCombiner.Transforms
             }.Schedule(_bufferCombiner.TransformAccessArray, handle);
 
+            _bufferCombiner.FlipBuffer();
+
             handle = new UpdateFastSpringBoneJob
             {
-                Colliders = _bufferCombiner.Colliders,
                 Joints = _bufferCombiner.Joints,
                 Logics = _bufferCombiner.Logics,
+                CurrentTail = _bufferCombiner.CurrentTails,
+                PrevTail = _bufferCombiner.PrevTails,
+                NextTail = _bufferCombiner.NextTails,
                 Springs = _bufferCombiner.Springs,
+                Colliders = _bufferCombiner.Colliders,
                 Transforms = _bufferCombiner.Transforms,
                 DeltaTime = deltaTime,
             }.Schedule(_bufferCombiner.Springs.Length, 1, handle);
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs
index 99785caf8..35b36dbd8 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs
@@ -16,9 +16,9 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
     {
         // NOTE: これらはFastSpringBoneBufferCombinerによってバッチングされる
         public NativeArray<BlittableSpring> Springs { get; }
-        public NativeArray<BlittableJoint> Joints { get; }
+        public NativeArray<BlittableJointMutable> Joints { get; }
         public NativeArray<BlittableCollider> Colliders { get; }
-        public NativeArray<BlittableLogic> Logics { get; }
+        public NativeArray<BlittableJointImmutable> Logics { get; }
         public NativeArray<BlittableTransform> BlittableTransforms { get; }
         public Transform[] Transforms { get; }
         public bool IsDisposed { get; private set; }
@@ -92,9 +92,9 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
 
             var externalDataPtr = (BlittableExternalData*)_externalData.GetUnsafePtr();
             List<BlittableSpring> blittableSprings = new();
-            List<BlittableJoint> blittableJoints = new();
+            List<BlittableJointMutable> blittableJoints = new();
             List<BlittableCollider> blittableColliders = new();
-            List<BlittableLogic> blittableLogics = new();
+            List<BlittableJointImmutable> blittableLogics = new();
             foreach (var spring in springs)
             {
                 var blittableSpring = new BlittableSpring
@@ -131,9 +131,9 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
             }
 
             Springs = new NativeArray<BlittableSpring>(blittableSprings.ToArray(), Allocator.Persistent);
-            Joints = new NativeArray<BlittableJoint>(blittableJoints.ToArray(), Allocator.Persistent);
+            Joints = new NativeArray<BlittableJointMutable>(blittableJoints.ToArray(), Allocator.Persistent);
             Colliders = new NativeArray<BlittableCollider>(blittableColliders.ToArray(), Allocator.Persistent);
-            Logics = new NativeArray<BlittableLogic>(blittableLogics.ToArray(), Allocator.Persistent);
+            Logics = new NativeArray<BlittableJointImmutable>(blittableLogics.ToArray(), Allocator.Persistent);
             BlittableTransforms = new NativeArray<BlittableTransform>(Transforms.Length, Allocator.Persistent);
             Profiler.EndSample();
         }
@@ -145,15 +145,17 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
         /// <param name="spring"></param>
         /// <param name="i">joint index</param>
         /// <returns></returns>
-        public static IEnumerable<BlittableLogic> LogicFromTransform(Transform[] Transforms, FastSpringBoneSpring spring)
+        public static IEnumerable<BlittableJointImmutable> LogicFromTransform(Transform[] Transforms, FastSpringBoneSpring spring)
         {
             // vrm-1.0 では末端の joint は tail で処理対象でないのに注意!
             for (int i = 0; i < spring.joints.Length - 1; ++i)
             {
                 var joint = spring.joints[i];
-                var tailJoint = i + 1 < spring.joints.Length ? spring.joints[i + 1] : (FastSpringBoneJoint?)null;
+                Debug.Assert(i + 1 < spring.joints.Length);
+                var tailJoint = (i + 1 < spring.joints.Length) ? spring.joints[i + 1] : (FastSpringBoneJoint?)null;
+                Debug.Assert(tailJoint.HasValue);
                 var parentJoint = i - 1 >= 0 ? spring.joints[i - 1] : (FastSpringBoneJoint?)null;
-                var localPosition = Vector3.zero;
+                Vector3 localPosition;
                 if (tailJoint.HasValue)
                 {
                     localPosition = tailJoint.Value.Transform.localPosition;
@@ -178,19 +180,13 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
                         localPosition.y * scale.y,
                         localPosition.z * scale.z
                     );
-
-                var worldChildPosition = joint.Transform.TransformPoint(localChildPosition);
-                var currentTail = spring.center != null
-                    ? spring.center.InverseTransformPoint(worldChildPosition)
-                    : worldChildPosition;
                 var parent = joint.Transform.parent;
 
-                yield return new BlittableLogic
+                yield return new BlittableJointImmutable
                 {
                     headTransformIndex = Array.IndexOf(Transforms, joint.Transform),
                     parentTransformIndex = Array.IndexOf(Transforms, parent),
-                    currentTail = currentTail,
-                    prevTail = currentTail, // same with currentTail. velocity zero.
+                    tailTransformIndex = Array.IndexOf(Transforms, tailJoint.Value),
                     localRotation = joint.DefaultLocalRotation,
                     boneAxis = localChildPosition.normalized,
                     length = localChildPosition.magnitude
@@ -209,16 +205,5 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
             Logics.Dispose();
             _externalData.Dispose();
         }
-
-        public void SyncAndZeroVelocity(IReadOnlyList<BlittableLogic> logics)
-        {
-            var dst = Logics;
-            for (int i = 0; i < logics.Count; ++i)
-            {
-                var l = logics[i];
-                l.prevTail = l.currentTail;
-                dst[i] = l;
-            }
-        }
     }
 }
\ No newline at end of file
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneJoint.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneJoint.cs
index 69cb51a80..2d8a0119d 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneJoint.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneJoint.cs
@@ -8,7 +8,7 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
     public struct FastSpringBoneJoint
     {
         public Transform Transform;
-        public BlittableJoint Joint;
+        public BlittableJointMutable Joint;
         public Quaternion DefaultLocalRotation;
     }
 }
\ No newline at end of file
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/UpdateFastSpringBoneJob.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/UpdateFastSpringBoneJob.cs
index 05011e8f0..c6d0e2f9a 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/UpdateFastSpringBoneJob.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/UpdateFastSpringBoneJob.cs
@@ -14,11 +14,21 @@ namespace UniGLTF.SpringBoneJobs
 #endif
     public struct UpdateFastSpringBoneJob : IJobParallelFor
     {
+        // すべての spring の joint を平坦に連結した配列
+        // Joints, Logics, PrevTail, CurrentTail, NextTail は同じ index
+        [ReadOnly] public NativeArray<BlittableJointMutable> Joints;
+        [ReadOnly] public NativeArray<BlittableJointImmutable> Logics;
+        [ReadOnly] public NativeArray<Vector3> PrevTail;
+        [ReadOnly] public NativeArray<Vector3> CurrentTail;
+        // ランダムアクセス
+        [NativeDisableParallelForRestriction] public NativeArray<Vector3> NextTail;
+
         [ReadOnly] public NativeArray<BlittableSpring> Springs;
-        [ReadOnly] public NativeArray<BlittableJoint> Joints;
+
         [ReadOnly] public NativeArray<BlittableCollider> Colliders;
 
-        [NativeDisableParallelForRestriction] public NativeArray<BlittableLogic> Logics;
+        // FastSpringBoneBuffer.Transforms を連結したもの
+        // ランダムアクセス
         [NativeDisableParallelForRestriction] public NativeArray<BlittableTransform> Transforms;
 
         public float DeltaTime;
@@ -52,11 +62,11 @@ namespace UniGLTF.SpringBoneJobs
                 }
 
                 var currentTail = centerTransform.HasValue
-                    ? centerTransform.Value.localToWorldMatrix.MultiplyPoint3x4(logic.currentTail)
-                    : logic.currentTail;
+                    ? centerTransform.Value.localToWorldMatrix.MultiplyPoint3x4(CurrentTail[logicIndex])
+                    : CurrentTail[logicIndex];
                 var prevTail = centerTransform.HasValue
-                    ? centerTransform.Value.localToWorldMatrix.MultiplyPoint3x4(logic.prevTail)
-                    : logic.prevTail;
+                    ? centerTransform.Value.localToWorldMatrix.MultiplyPoint3x4(PrevTail[logicIndex])
+                    : PrevTail[logicIndex];
 
                 var parentRotation = parentTransform?.rotation ?? Quaternion.identity;
 
@@ -108,14 +118,10 @@ namespace UniGLTF.SpringBoneJobs
                     }
                 }
 
-                logic.prevTail = centerTransform.HasValue
-                    ? centerTransform.Value.worldToLocalMatrix.MultiplyPoint3x4(currentTail)
-                    : currentTail;
-                logic.currentTail = centerTransform.HasValue
+                NextTail[logicIndex] = centerTransform.HasValue
                     ? centerTransform.Value.worldToLocalMatrix.MultiplyPoint3x4(nextTail)
                     : nextTail;
 
-
                 //回転を適用
                 var rotation = parentRotation * logic.localRotation;
                 headTransform.rotation = Quaternion.FromToRotation(rotation * logic.boneAxis,
@@ -157,7 +163,6 @@ namespace UniGLTF.SpringBoneJobs
                     // SpringBone の結果を Transform に反映しないが logic の更新は継続する。
                     // 再開したときに暴れない。
                 }
-                Logics[logicIndex] = logic;
             }
         }
 
@@ -174,10 +179,10 @@ namespace UniGLTF.SpringBoneJobs
             Vector3 worldTail,
             Vector3 worldPosition,
             BlittableTransform headTransform,
-            BlittableJoint joint,
+            BlittableJointMutable joint,
             BlittableCollider collider,
             float maxColliderScale,
-            BlittableLogic logic,
+            BlittableJointImmutable logic,
             ref Vector3 nextTail)
         {
             var direction = worldTail - worldPosition;
@@ -209,12 +214,12 @@ namespace UniGLTF.SpringBoneJobs
         }
 
         private static void ResolveSphereCollision(
-            BlittableJoint joint,
+            BlittableJointMutable joint,
             BlittableCollider collider,
             Vector3 worldPosition,
             BlittableTransform headTransform,
             float maxColliderScale,
-            BlittableLogic logic,
+            BlittableJointImmutable logic,
             ref Vector3 nextTail)
         {
             var r = joint.radius + collider.radius * maxColliderScale;
@@ -229,7 +234,7 @@ namespace UniGLTF.SpringBoneJobs
         }
 
         private static void ResolveSphereCollisionInside(
-            BlittableJoint joint,
+            BlittableJointMutable joint,
             BlittableCollider collider,
             BlittableTransform colliderTransform,
             ref Vector3 nextTail)
@@ -249,7 +254,7 @@ namespace UniGLTF.SpringBoneJobs
         }
 
         private static void ResolveCapsuleCollisionInside(
-            BlittableJoint joint,
+            BlittableJointMutable joint,
             BlittableCollider collider,
             BlittableTransform colliderTransform,
             ref Vector3 nextTail)
@@ -298,7 +303,7 @@ namespace UniGLTF.SpringBoneJobs
         /// <param name="colliderTransform">colliderTransform.localToWorldMatrix.MultiplyPoint3x4(collider.offset);</param>
         /// <param name="nextTail">result of verlet integration</param>
         private static void ResolvePlaneCollision(
-            BlittableJoint joint,
+            BlittableJointMutable joint,
             BlittableCollider collider,
             BlittableTransform colliderTransform,
             ref Vector3 nextTail)
diff --git a/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs b/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs
index fc6a9a4a2..e7c32945b 100644
--- a/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs
+++ b/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs
@@ -87,7 +87,7 @@ namespace VRM.SpringBoneJobs
             joints.Add(new FastSpringBoneJoint
             {
                 Transform = joint.transform,
-                Joint = new BlittableJoint
+                Joint = new BlittableJointMutable
                 {
                     radius = spring.m_hitRadius,
                     dragForce = spring.m_dragForce,
diff --git a/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeSpringBone.cs b/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeSpringBone.cs
index 9e0819b6a..d14e0e9e7 100644
--- a/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeSpringBone.cs
+++ b/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeSpringBone.cs
@@ -92,7 +92,7 @@ namespace UniVRM10
                    .Select(joint => new FastSpringBoneJoint
                    {
                        Transform = joint.transform,
-                       Joint = new BlittableJoint
+                       Joint = new BlittableJointMutable
                        {
                            radius = joint.m_jointRadius,
                            dragForce = joint.m_dragForce,
@@ -150,15 +150,7 @@ namespace UniVRM10
                 transform.localRotation = m_initialLocalRotations[i];
             }
 
-            // 初期状態にしたtransformを使って spring logic を構築
-            List<BlittableLogic> blittableLogics = new();
-            foreach (var spring in m_springs)
-            {
-                blittableLogics.AddRange(
-                    FastSpringBoneBuffer.LogicFromTransform(m_fastSpringBoneBuffer.Transforms, spring));
-            }
-            // DOTS バッファーを更新
-            m_fastSpringBoneBuffer.SyncAndZeroVelocity(blittableLogics);
+            // TODO:
         }
     }
 }
\ No newline at end of file