diff --git a/Assets/VRM10/Runtime/Components/Constraint/TR.cs b/Assets/VRM10/Runtime/Components/Constraint/TR.cs
index 14466898f..7a393f267 100644
--- a/Assets/VRM10/Runtime/Components/Constraint/TR.cs
+++ b/Assets/VRM10/Runtime/Components/Constraint/TR.cs
@@ -36,5 +36,11 @@ namespace UniVRM10
         public Matrix4x4 TRS(float s) => Matrix4x4.TRS(Translation, Rotation, new Vector3(s, s, s));
 
         public static TR operator *(TR a, TR b) => new TR(a.Rotation * b.Rotation, a.Rotation * b.Translation + a.Translation);
+
+        public TR Inverse()
+        {
+            var inv = Quaternion.Inverse(Rotation);
+            return new TR(inv, inv * Translation);
+        }
     }
 }