diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SceneInfo.cs b/Assets/VRM/Runtime/SpringBone/Logic/SceneInfo.cs
index 546673013..15053e9d2 100644
--- a/Assets/VRM/Runtime/SpringBone/Logic/SceneInfo.cs
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SceneInfo.cs
@@ -3,10 +3,16 @@ using UnityEngine;
 
 namespace VRM.SpringBone
 {
-    struct SceneInfo
+    readonly struct SceneInfo
     {
-        public IReadOnlyList<Transform> RootBones;
-        public Transform Center;
-        public VRMSpringBoneColliderGroup[] ColliderGroups;
+        public readonly IReadOnlyList<Transform> RootBones;
+        public readonly Transform Center;
+        public readonly VRMSpringBoneColliderGroup[] ColliderGroups;
+
+        public SceneInfo(
+            IReadOnlyList<Transform> rootBones,
+            Transform center,
+            VRMSpringBoneColliderGroup[] colliderGroups) =>
+                (RootBones, Center, ColliderGroups) = (rootBones, center, colliderGroups);
     }
 }
\ No newline at end of file
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SphereCollider.cs b/Assets/VRM/Runtime/SpringBone/Logic/SphereCollider.cs
index a59c36e8c..ded97a744 100644
--- a/Assets/VRM/Runtime/SpringBone/Logic/SphereCollider.cs
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SphereCollider.cs
@@ -2,7 +2,7 @@ using UnityEngine;
 
 namespace VRM.SpringBone
 {
-    struct SphereCollider
+    readonly struct SphereCollider
     {
         public readonly Vector3 Position;
         public readonly float Radius;
@@ -14,5 +14,23 @@ namespace VRM.SpringBone
             var scale = Mathf.Max(Mathf.Max(ls.x, ls.y), ls.z);
             Radius = scale * collider.Radius;
         }
+
+        public bool TryCollide(SpringBoneSettings settings, Transform transform, Vector3 nextTail, out Vector3 posFromCollider)
+        {
+            var m_radius = settings.HitRadius * transform.UniformedLossyScale();
+            var r = m_radius + Radius;
+            if (Vector3.SqrMagnitude(nextTail - Position) <= (r * r))
+            {
+                // ヒット。Colliderの半径方向に押し出す
+                var normal = (nextTail - Position).normalized;
+                posFromCollider = Position + normal * (m_radius + Radius);
+                return true;
+            }
+            else
+            {
+                posFromCollider = default;
+                return false;
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJoint.cs b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJoint.cs
deleted file mode 100644
index d15e48201..000000000
--- a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJoint.cs
+++ /dev/null
@@ -1,129 +0,0 @@
-using System.Collections.Generic;
-using UnityEngine;
-
-namespace VRM.SpringBone
-{
-    /// <summary>
-    /// original from
-    /// http://rocketjump.skr.jp/unity3d/109/
-    /// </summary>
-    class SpringBoneJoint
-    {
-        Transform m_transform;
-        public Transform Head => m_transform;
-
-        private Vector3 m_boneAxis;
-        private Vector3 m_currentTail;
-
-        private readonly float m_length;
-        private Vector3 m_localDir;
-        private Vector3 m_prevTail;
-
-        public SpringBoneJoint(Transform center, Transform transform, Vector3 localChildPosition)
-        {
-            m_transform = transform;
-            var worldChildPosition = m_transform.TransformPoint(localChildPosition);
-            m_currentTail = center != null
-                    ? center.InverseTransformPoint(worldChildPosition)
-                    : worldChildPosition;
-            m_prevTail = m_currentTail;
-            LocalRotation = transform.localRotation;
-            m_boneAxis = localChildPosition.normalized;
-            m_length = localChildPosition.magnitude;
-        }
-
-        public Vector3 Tail => m_transform.localToWorldMatrix.MultiplyPoint(m_boneAxis * m_length);
-
-        private Quaternion LocalRotation { get; }
-
-        float m_radius;
-        public void SetRadius(float radius)
-        {
-            m_radius = radius * m_transform.UniformedLossyScale();
-        }
-
-        private Quaternion ParentRotation =>
-            m_transform.parent != null
-                ? m_transform.parent.rotation
-                : Quaternion.identity;
-
-        public void Update(Transform center,
-            float stiffnessForce, float dragForce, Vector3 external,
-            List<SphereCollider> colliders)
-        {
-            var currentTail = center != null
-                    ? center.TransformPoint(m_currentTail)
-                    : m_currentTail;
-            var prevTail = center != null
-                    ? center.TransformPoint(m_prevTail)
-                    : m_prevTail;
-
-            // verlet積分で次の位置を計算
-            var nextTail = currentTail
-                           + (currentTail - prevTail) * (1.0f - dragForce) // 前フレームの移動を継続する(減衰もあるよ)
-                           + ParentRotation * LocalRotation * m_boneAxis * stiffnessForce // 親の回転による子ボーンの移動目標
-                           + external; // 外力による移動量
-
-            // 長さをboneLengthに強制
-            var position = m_transform.position;
-            nextTail = position + (nextTail - position).normalized * m_length;
-
-            // Collisionで移動
-            nextTail = Collision(colliders, nextTail);
-
-            m_prevTail = center != null
-                    ? center.InverseTransformPoint(currentTail)
-                    : currentTail;
-
-            m_currentTail = center != null
-                    ? center.InverseTransformPoint(nextTail)
-                    : nextTail;
-
-            //回転を適用
-            m_transform.rotation = ApplyRotation(nextTail);
-        }
-
-        protected virtual Quaternion ApplyRotation(Vector3 nextTail)
-        {
-            var rotation = ParentRotation * LocalRotation;
-            return Quaternion.FromToRotation(rotation * m_boneAxis,
-                       nextTail - m_transform.position) * rotation;
-        }
-
-        protected virtual Vector3 Collision(List<SpringBone.SphereCollider> colliders, Vector3 nextTail)
-        {
-            foreach (var collider in colliders)
-            {
-                var r = m_radius + collider.Radius;
-                if (Vector3.SqrMagnitude(nextTail - collider.Position) <= (r * r))
-                {
-                    // ヒット。Colliderの半径方向に押し出す
-                    var normal = (nextTail - collider.Position).normalized;
-                    var posFromCollider = collider.Position + normal * (m_radius + collider.Radius);
-                    // 長さをboneLengthに強制
-                    nextTail = m_transform.position + (posFromCollider - m_transform.position).normalized * m_length;
-                }
-            }
-            return nextTail;
-        }
-
-        public void DrawGizmo(Transform center, Color color)
-        {
-            var currentTail = center != null
-                    ? center.TransformPoint(m_currentTail)
-                    : m_currentTail;
-            var prevTail = center != null
-                    ? center.TransformPoint(m_prevTail)
-                    : m_prevTail;
-
-            Gizmos.color = Color.gray;
-            Gizmos.DrawLine(currentTail, prevTail);
-            Gizmos.DrawWireSphere(prevTail, m_radius);
-
-            Gizmos.color = color;
-            Gizmos.DrawLine(currentTail, m_transform.position);
-            Gizmos.DrawWireSphere(currentTail, m_radius);
-        }
-    }
-
-}
\ No newline at end of file
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointInit.cs b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointInit.cs
new file mode 100644
index 000000000..6b2b92ce0
--- /dev/null
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointInit.cs
@@ -0,0 +1,64 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace VRM.SpringBone
+{
+    /// <summary>
+    /// original from
+    /// http://rocketjump.skr.jp/unity3d/109/
+    /// 
+    /// この型のフィールドはSpringBoneのライフサイクルを通じて不変。
+    /// </summary>
+    readonly struct SpringBoneJointInit
+    {
+        public readonly Vector3 BoneAxis;
+        public readonly float Length;
+        public readonly Quaternion LocalRotation;
+
+        public SpringBoneJointInit(
+        Vector3 boneAxis,
+        float length,
+        Quaternion localRotation) => (BoneAxis, Length, LocalRotation) = (boneAxis, length, localRotation);
+
+        /// <summary>
+        /// しっぽの位置から回転を計算する
+        /// </summary>
+        public Quaternion WorldRotationFromTailPosition(Transform m_transform, Vector3 nextTail)
+        {
+            var rotation = (m_transform.parent != null ? m_transform.parent.rotation : Quaternion.identity) * LocalRotation;
+            return Quaternion.FromToRotation(rotation * BoneAxis,
+                       nextTail - m_transform.position) * rotation;
+        }
+
+        /// <summary>
+        /// Verlet積分で次の位置を計算する
+        /// </summary>
+        public Vector3 VerletIntegration(float deltaTime, Transform center, Quaternion parentRotation,
+            SpringBoneSettings settings, SpringBoneJointState _state)
+        {
+            var state = _state.ToWorld(center);
+
+            // verlet積分で次の位置を計算
+            var nextTail = state.CurrentTail
+                           + (state.CurrentTail - state.PrevTail) * (1.0f - settings.DragForce) // 前フレームの移動を継続する(減衰もあるよ)
+                           + parentRotation * LocalRotation * BoneAxis * settings.StiffnessForce * deltaTime // 親の回転による子ボーンの移動目標
+                           + settings.GravityDir * (settings.GravityPower * deltaTime); // 外力による移動量
+            return nextTail;
+        }
+
+        public void DrawGizmo(Transform center, Transform m_transform, SpringBoneSettings settings, Color color, SpringBoneJointState m_state)
+        {
+            var state = m_state.ToWorld(center);
+            var m_radius = settings.HitRadius * m_transform.UniformedLossyScale();
+
+            Gizmos.color = Color.gray;
+            Gizmos.DrawLine(state.CurrentTail, state.PrevTail);
+            Gizmos.DrawWireSphere(state.PrevTail, m_radius);
+
+            Gizmos.color = color;
+            Gizmos.DrawLine(state.CurrentTail, m_transform.position);
+            Gizmos.DrawWireSphere(state.CurrentTail, m_radius);
+        }
+
+    };
+}
\ No newline at end of file
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJoint.cs.meta b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointInit.cs.meta
similarity index 100%
rename from Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJoint.cs.meta
rename to Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointInit.cs.meta
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointState.cs b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointState.cs
new file mode 100644
index 000000000..31bde5ea7
--- /dev/null
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointState.cs
@@ -0,0 +1,49 @@
+using UnityEngine;
+
+namespace VRM.SpringBone
+{
+    /// <summary>
+    /// 毎フレーム更新される Verlet 積分の位置状態
+    /// </summary>
+    readonly struct SpringBoneJointState
+    {
+        public readonly Vector3 CurrentTail;
+        public readonly Vector3 PrevTail;
+
+        public SpringBoneJointState(Vector3 currentTail, Vector3 prevTail) =>
+            (CurrentTail, PrevTail) = (currentTail, prevTail);
+
+        public static SpringBoneJointState Init(Transform center, Transform transform, Vector3 localChildPosition)
+        {
+            var worldChildPosition = transform.TransformPoint(localChildPosition);
+            var tail = center != null
+                    ? center.InverseTransformPoint(worldChildPosition)
+                    : worldChildPosition;
+            return new SpringBoneJointState(currentTail: tail, prevTail: tail);
+        }
+
+        public static SpringBoneJointState Make(Transform center, Vector3 currentTail, Vector3 nextTail)
+        {
+            return new SpringBoneJointState
+            (
+                prevTail: center != null
+                    ? center.InverseTransformPoint(currentTail)
+                    : currentTail,
+                currentTail: center != null
+                    ? center.InverseTransformPoint(nextTail)
+                    : nextTail);
+        }
+
+        public SpringBoneJointState ToWorld(Transform center)
+        {
+            return new SpringBoneJointState
+            (
+                currentTail: center != null
+                    ? center.TransformPoint(CurrentTail)
+                    : CurrentTail,
+                prevTail: center != null
+                    ? center.TransformPoint(PrevTail)
+                    : PrevTail);
+        }
+    };
+}
\ No newline at end of file
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointState.cs.meta b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointState.cs.meta
new file mode 100644
index 000000000..b68add524
--- /dev/null
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneJointState.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 3bbcafd66c035184b8aa868b65c01c1d
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSettings.cs b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSettings.cs
index bc6209047..8ddabf49d 100644
--- a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSettings.cs
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSettings.cs
@@ -2,12 +2,15 @@ using UnityEngine;
 
 namespace VRM.SpringBone
 {
-    struct SpringBoneSettings
+    readonly struct SpringBoneSettings
     {
-        public float StiffnessForce;
-        public Vector3 GravityDir;
-        public float GravityPower;
-        public float HitRadius;
-        public float DragForce;
+        public readonly float StiffnessForce;
+        public readonly float DragForce;
+        public readonly Vector3 GravityDir;
+        public readonly float GravityPower;
+        public readonly float HitRadius;
+
+        public SpringBoneSettings(float stiffnessForce, float dragForce, Vector3 gravityDir, float gravityPower, float hitRadius) =>
+            (StiffnessForce, DragForce, GravityDir, GravityPower, HitRadius) = (stiffnessForce, dragForce, gravityDir, gravityPower, hitRadius);
     }
 }
\ No newline at end of file
diff --git a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSystem.cs b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSystem.cs
index 98d5d433d..1badea980 100644
--- a/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSystem.cs
+++ b/Assets/VRM/Runtime/SpringBone/Logic/SpringBoneSystem.cs
@@ -4,25 +4,12 @@ using UnityEngine;
 
 namespace VRM.SpringBone
 {
-    /// <summary>
-    /// 同じ設定のスプリングをまとめて処理する。
-    /// 
-    /// root o-o-o-x tail
-    /// 
-    /// [vrm0] tail は 7cm 遠にダミーの joint があるようにふるまう。
-    /// 
-    /// </summary>
     class SpringBoneSystem
     {
         Dictionary<Transform, Quaternion> m_initialLocalRotationMap;
-        List<SpringBoneJoint> m_joints = new();
+        List<(Transform, SpringBoneJointInit, SpringBoneJointState)> m_joints = new();
         List<SphereCollider> m_colliders = new();
 
-        public void SetLocalRotationsIdentity()
-        {
-            foreach (var verlet in m_joints) verlet.Head.localRotation = Quaternion.identity;
-        }
-
         public void Setup(SceneInfo scene, bool force)
         {
             if (force || m_initialLocalRotationMap == null)
@@ -54,8 +41,8 @@ namespace VRM.SpringBone
 
         private void SetupRecursive(Transform center, Transform parent)
         {
-            Vector3 localPosition = default;
-            Vector3 scale = default;
+            Vector3 localPosition;
+            Vector3 scale;
             if (parent.childCount == 0)
             {
                 // 子ノードが無い。7cm 固定
@@ -70,18 +57,25 @@ namespace VRM.SpringBone
                 localPosition = firstChild.localPosition;
                 scale = firstChild.lossyScale;
             }
-            m_joints.Add(new SpringBone.SpringBoneJoint(center, parent,
-                    new Vector3(
+
+            var localChildPosition = new Vector3(
                         localPosition.x * scale.x,
                         localPosition.y * scale.y,
                         localPosition.z * scale.z
-                    )))
-                ;
+                    );
+            m_joints.Add((
+                parent,
+                new SpringBoneJointInit
+                (
+                    localRotation: parent.localRotation,
+                    boneAxis: localChildPosition.normalized,
+                    length: localChildPosition.magnitude
+                ),
+                SpringBoneJointState.Init(center, parent, localChildPosition)));
 
             foreach (Transform child in parent) SetupRecursive(center, child);
         }
 
-
         public void UpdateProcess(float deltaTime,
             SceneInfo scene,
             SpringBoneSettings settings
@@ -93,6 +87,7 @@ namespace VRM.SpringBone
                 Setup(scene, false);
             }
 
+            // collider の収集
             m_colliders.Clear();
             if (scene.ColliderGroups != null)
             {
@@ -108,26 +103,39 @@ namespace VRM.SpringBone
                 }
             }
 
-            var stiffness = settings.StiffnessForce * deltaTime;
-            var external = settings.GravityDir * (settings.GravityPower * deltaTime);
-
-            foreach (var verlet in m_joints)
+            for (int i = 0; i < m_joints.Count; ++i)
             {
-                verlet.SetRadius(settings.HitRadius);
-                verlet.Update(scene.Center,
-                    stiffness,
-                    settings.DragForce,
-                    external,
-                    m_colliders
-                );
+                var (transform, init, state) = m_joints[i];
+
+                // Spring処理
+                var parentRotation = (transform.parent != null ? transform.parent.rotation : Quaternion.identity);
+                var nextTail = init.VerletIntegration(deltaTime, scene.Center, parentRotation, settings, state);
+
+                // 長さをboneLengthに強制
+                nextTail = transform.position + (nextTail - transform.position).normalized * init.Length;
+
+                // Collision
+                foreach (var collider in m_colliders)
+                {
+                    if (collider.TryCollide(settings, transform, nextTail, out var posFromCollider))
+                    {
+                        // 長さをboneLengthに強制
+                        nextTail = transform.position + (posFromCollider - transform.position).normalized * init.Length;
+                    }
+                }
+
+                // 状態更新
+                m_joints[i] = (transform, init, SpringBoneJointState.Make(scene.Center, currentTail: state.CurrentTail, nextTail: nextTail));
+                //回転を適用
+                transform.rotation = init.WorldRotationFromTailPosition(transform, nextTail);
             }
         }
 
-        public void PlayingGizmo(Transform m_center, Color m_gizmoColor)
+        public void PlayingGizmo(Transform m_center, SpringBoneSettings settings, Color m_gizmoColor)
         {
-            foreach (var verlet in m_joints)
+            foreach (var (transform, init, state) in m_joints)
             {
-                verlet.DrawGizmo(m_center, m_gizmoColor);
+                init.DrawGizmo(m_center, transform, settings, m_gizmoColor, state);
             }
         }
 
diff --git a/Assets/VRM/Runtime/SpringBone/VRMSpringBone.cs b/Assets/VRM/Runtime/SpringBone/VRMSpringBone.cs
index 2e971d2cc..9932e3394 100644
--- a/Assets/VRM/Runtime/SpringBone/VRMSpringBone.cs
+++ b/Assets/VRM/Runtime/SpringBone/VRMSpringBone.cs
@@ -37,15 +37,17 @@ namespace VRM
             Setup();
         }
 
-        SpringBone.SceneInfo Scene => new SpringBone.SceneInfo { RootBones = RootBones, Center = m_center };
-        SpringBone.SpringBoneSettings Settings => new SpringBone.SpringBoneSettings
-        {
-            StiffnessForce = m_stiffnessForce,
-            GravityDir = m_gravityDir,
-            GravityPower = m_gravityPower,
-            HitRadius = m_hitRadius,
-            DragForce = m_dragForce,
-        };
+        SpringBone.SceneInfo Scene => new(
+            rootBones: RootBones,
+            center: m_center,
+            colliderGroups: ColliderGroups);
+        SpringBone.SpringBoneSettings Settings => new
+        (
+            stiffnessForce: m_stiffnessForce,
+            dragForce: m_dragForce,
+            gravityDir: m_gravityDir,
+            gravityPower: m_gravityPower,
+            hitRadius: m_hitRadius);
 
         [ContextMenu("Reset bones")]
         public void Setup(bool force = false)
@@ -85,7 +87,7 @@ namespace VRM
         {
             if (Application.isPlaying)
             {
-                m_system.PlayingGizmo(m_center, m_gizmoColor);
+                m_system.PlayingGizmo(m_center, Settings, m_gizmoColor);
             }
             else
             {