diff --git a/Assets/VRM10/Runtime/UnityExtensions.cs b/Assets/VRM10/Runtime/UnityExtensions.cs
index 0b340736a..936d2bcf8 100644
--- a/Assets/VRM10/Runtime/UnityExtensions.cs
+++ b/Assets/VRM10/Runtime/UnityExtensions.cs
@@ -106,6 +106,10 @@ namespace UniVRM10
 
         public static Matrix4x4 RotateY180(this Matrix4x4 m)
         {
+            // R, R, R, 0
+            // R, R, R, 0
+            // R, R, R, 0
+            // T, T, T, 1
             var t = m.GetRow(3);
             var tt = RotateY180(t);
             m.SetRow(3, tt);
diff --git a/Assets/VRM10/vrmlib/Runtime/NumericsExtensions.cs b/Assets/VRM10/vrmlib/Runtime/NumericsExtensions.cs
index c83e121f4..54a5434f0 100644
--- a/Assets/VRM10/vrmlib/Runtime/NumericsExtensions.cs
+++ b/Assets/VRM10/vrmlib/Runtime/NumericsExtensions.cs
@@ -133,7 +133,10 @@ namespace VrmLib
             if (m.IsOnlyTranslation())
             {
                 var ret = m;
-                // M4x に移動が入っている
+                // R, R, R, 0
+                // R, R, R, 0
+                // R, R, R, 0
+                // T, T, T, 1
                 ret.M43 = -ret.M43;
                 return ret;
             }
@@ -149,7 +152,10 @@ namespace VrmLib
             if (m.IsOnlyTranslation())
             {
                 var ret = m;
-                // M4x に移動が入っている
+                // R, R, R, 0
+                // R, R, R, 0
+                // R, R, R, 0
+                // T, T, T, 1
                 ret.M41 = -ret.M41;
                 return ret;
             }
diff --git a/Assets/VRM10/vrmlib/Runtime/SpanLike.cs b/Assets/VRM10/vrmlib/Runtime/SpanLike.cs
index 8efe27fa4..aa0a39965 100644
--- a/Assets/VRM10/vrmlib/Runtime/SpanLike.cs
+++ b/Assets/VRM10/vrmlib/Runtime/SpanLike.cs
@@ -438,6 +438,9 @@ namespace VrmLib
             }},
             {typeof(UnityEngine.Matrix4x4), new GetSet<UnityEngine.Matrix4x4>{
                 Getter = (array, start) =>
+                    // UnityEngine.Matrix4x4
+                    // * 列優先メモリレイアウト(col0, col1, col2, col3)
+                    // * Constructor 引き数が行優先 new Matrix4x4(row0, row1, row2, row3);
                     new UnityEngine.Matrix4x4(
                         new UnityEngine.Vector4(BitConverter.ToSingle(array, start),
                         BitConverter.ToSingle(array, start + 16),