diff --git a/Assets/UniGLTF/Runtime/Extensions/KeyValuePairExtensions.cs b/Assets/UniGLTF/Runtime/Extensions/KeyValuePairExtensions.cs
new file mode 100644
index 000000000..5f94c8101
--- /dev/null
+++ b/Assets/UniGLTF/Runtime/Extensions/KeyValuePairExtensions.cs
@@ -0,0 +1,13 @@
+using System.Collections.Generic;
+
+namespace UniGLTF
+{
+    public static class KeyValuePairExtensions
+    {
+        public static void Deconstruct<T, U>(this KeyValuePair<T, U> pair, out T key, out U value)
+        {
+            key = pair.Key;
+            value = pair.Value;
+        }
+    }
+}
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/SpanLike.cs.meta b/Assets/UniGLTF/Runtime/Extensions/KeyValuePairExtensions.cs.meta
similarity index 83%
rename from Assets/UniGLTF/Runtime/UniGLTF/IO/SpanLike.cs.meta
rename to Assets/UniGLTF/Runtime/Extensions/KeyValuePairExtensions.cs.meta
index ec2ce3377..022151d5f 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/SpanLike.cs.meta
+++ b/Assets/UniGLTF/Runtime/Extensions/KeyValuePairExtensions.cs.meta
@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: 8ef774aa861dc6f46a94330c7169bf04
+guid: be00d5fb3e17dbf4e87ec4a7aae8dbc3
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/SpanLike.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/SpanLike.cs
deleted file mode 100644
index 71ce55e5f..000000000
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/SpanLike.cs
+++ /dev/null
@@ -1,492 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Runtime.InteropServices;
-
-namespace UniGLTF
-{
-    static class BitWriter
-    {
-        public static void Write(byte[] bytes, int i, Int32 value)
-        {
-            var tmp = BitConverter.GetBytes(value);
-            bytes[i++] = tmp[0];
-            bytes[i++] = tmp[1];
-            bytes[i++] = tmp[2];
-            bytes[i++] = tmp[3];
-        }
-
-        #region UINT
-        public static void Write(byte[] bytes, int i, Byte value)
-        {
-            bytes[i++] = value;
-        }
-
-        public static void Write(byte[] bytes, int i, UInt16 value)
-        {
-            var tmp = BitConverter.GetBytes(value);
-            bytes[i++] = tmp[0];
-            bytes[i++] = tmp[1];
-        }
-
-        public static void Write(byte[] bytes, int i, UInt32 value)
-        {
-            var tmp = BitConverter.GetBytes(value);
-            bytes[i++] = tmp[0];
-            bytes[i++] = tmp[1];
-            bytes[i++] = tmp[2];
-            bytes[i++] = tmp[3];
-        }
-        #endregion
-
-        public static void Write(byte[] bytes, int i, Single value)
-        {
-            var tmp = BitConverter.GetBytes(value);
-            bytes[i++] = tmp[0];
-            bytes[i++] = tmp[1];
-            bytes[i++] = tmp[2];
-            bytes[i++] = tmp[3];
-        }
-
-        public static void Write(byte[] bytes, int i, System.Numerics.Vector2 value)
-        {
-            Write(bytes, i, value.X);
-            Write(bytes, i + 4, value.Y);
-        }
-
-        public static void Write(byte[] bytes, int i, System.Numerics.Vector3 value)
-        {
-            Write(bytes, i, value.X);
-            Write(bytes, i + 4, value.Y);
-            Write(bytes, i + 8, value.Z);
-        }
-
-        public static void Write(byte[] bytes, int i, System.Numerics.Vector4 value)
-        {
-            Write(bytes, i, value.X);
-            Write(bytes, i + 4, value.Y);
-            Write(bytes, i + 8, value.Z);
-            Write(bytes, i + 12, value.W);
-        }
-
-        public static void Write(byte[] bytes, int i, System.Numerics.Quaternion value)
-        {
-            Write(bytes, i, value.X);
-            Write(bytes, i + 4, value.Y);
-            Write(bytes, i + 8, value.Z);
-            Write(bytes, i + 12, value.W);
-        }
-
-        public static void Write(byte[] bytes, int i, System.Numerics.Matrix4x4 value)
-        {
-            Write(bytes, i, value.M11);
-            Write(bytes, i + 4, value.M12);
-            Write(bytes, i + 8, value.M13);
-            Write(bytes, i + 12, value.M14);
-            Write(bytes, i + 16, value.M21);
-            Write(bytes, i + 20, value.M22);
-            Write(bytes, i + 24, value.M23);
-            Write(bytes, i + 28, value.M24);
-            Write(bytes, i + 32, value.M31);
-            Write(bytes, i + 36, value.M32);
-            Write(bytes, i + 40, value.M33);
-            Write(bytes, i + 44, value.M34);
-            Write(bytes, i + 48, value.M41);
-            Write(bytes, i + 52, value.M42);
-            Write(bytes, i + 56, value.M43);
-            Write(bytes, i + 60, value.M44);
-        }
-
-        public static void Write(byte[] bytes, int i, UShort4 value)
-        {
-            Write(bytes, i, value.x);
-            Write(bytes, i + 2, value.y);
-            Write(bytes, i + 4, value.z);
-            Write(bytes, i + 6, value.w);
-        }
-
-        public static void Write(byte[] bytes, int i, SkinJoints value)
-        {
-            Write(bytes, i, value.Joint0);
-            Write(bytes, i + 2, value.Joint1);
-            Write(bytes, i + 4, value.Joint2);
-            Write(bytes, i + 6, value.Joint3);
-        }
-
-        public static void Write(byte[] bytes, int i, Byte4 value)
-        {
-            bytes[i++] = value.x;
-            bytes[i++] = value.y;
-            bytes[i++] = value.z;
-            bytes[i++] = value.w;
-        }
-
-        public static void Write(byte[] bytes, int i, UnityEngine.Vector2 value)
-        {
-            Write(bytes, i, value.x);
-            Write(bytes, i + 4, value.y);
-        }
-
-        public static void Write(byte[] bytes, int i, UnityEngine.Vector3 value)
-        {
-            Write(bytes, i, value.x);
-            Write(bytes, i + 4, value.y);
-            Write(bytes, i + 8, value.z);
-        }
-
-        public static void Write(byte[] bytes, int i, UnityEngine.Vector4 value)
-        {
-            Write(bytes, i, value.x);
-            Write(bytes, i + 4, value.y);
-            Write(bytes, i + 8, value.z);
-            Write(bytes, i + 12, value.w);
-        }
-
-        public static void Write(byte[] bytes, int i, UnityEngine.Color value)
-        {
-            Write(bytes, i, value.r);
-            Write(bytes, i + 4, value.g);
-            Write(bytes, i + 8, value.b);
-            Write(bytes, i + 12, value.a);
-        }
-
-        public static void Write(byte[] bytes, int i, UnityEngine.Matrix4x4 value)
-        {
-            Write(bytes, i, value.m00);
-            Write(bytes, i + 4, value.m01);
-            Write(bytes, i + 8, value.m02);
-            Write(bytes, i + 12, value.m03);
-            Write(bytes, i + 16, value.m10);
-            Write(bytes, i + 20, value.m11);
-            Write(bytes, i + 24, value.m12);
-            Write(bytes, i + 28, value.m13);
-            Write(bytes, i + 32, value.m20);
-            Write(bytes, i + 36, value.m21);
-            Write(bytes, i + 40, value.m22);
-            Write(bytes, i + 44, value.m23);
-            Write(bytes, i + 48, value.m30);
-            Write(bytes, i + 52, value.m31);
-            Write(bytes, i + 56, value.m32);
-            Write(bytes, i + 60, value.m33);
-        }
-    }
-
-    public static class KeyValuePariExtensions
-    {
-        public static void Deconstruct<T, U>(this KeyValuePair<T, U> pair, out T key, out U value)
-        {
-            key = pair.Key;
-            value = pair.Value;
-        }
-    }
-
-    public struct SpanLike<T> : IEquatable<SpanLike<T>>, IEnumerable<T>
-    where T : struct
-    {
-        public readonly ArraySegment<byte> Bytes;
-
-        readonly int m_itemSize;
-        public readonly int Length;
-
-        public delegate T Getter(byte[] bytes, int start);
-        readonly Getter m_getter;
-
-        public delegate void Setter(byte[] bytes, int i, T value);
-        readonly Setter m_setter;
-
-        public T this[int i]
-        {
-            set
-            {
-                m_setter(Bytes.Array, Bytes.Offset + i * m_itemSize, value);
-            }
-            get
-            {
-                return m_getter(Bytes.Array, Bytes.Offset + i * m_itemSize);
-            }
-        }
-
-        public SpanLike(ArraySegment<byte> bytes, int itemSize, Getter getter, Setter setter)
-        {
-            Bytes = bytes;
-            m_itemSize = itemSize;
-            Length = Bytes.Count / m_itemSize;
-            m_getter = getter;
-            m_setter = setter;
-        }
-
-        public SpanLike<T> Slice(int offset, int count)
-        {
-            var bytesOffset = offset * m_itemSize;
-            var bytesLength = count * m_itemSize;
-            if (bytesOffset + bytesLength > Bytes.Count)
-            {
-                throw new ArgumentOutOfRangeException();
-            }
-            return new SpanLike<T>(new ArraySegment<byte>(
-                Bytes.Array,
-                Bytes.Offset + bytesOffset,
-                bytesLength
-            ), m_itemSize, m_getter, m_setter);
-        }
-
-        public SpanLike<T> Slice(int offset)
-        {
-            var bytesOffset = offset * m_itemSize;
-            if (bytesOffset > Bytes.Count)
-            {
-                throw new ArgumentOutOfRangeException();
-            }
-            var bytesLength = Bytes.Count - bytesOffset;
-            return new SpanLike<T>(new ArraySegment<byte>(
-                Bytes.Array,
-                Bytes.Offset + bytesOffset,
-                bytesLength
-            ), m_itemSize, m_getter, m_setter);
-        }
-
-        public T[] ToArray()
-        {
-            var array = new T[Length];
-            Bytes.FromBytes(array);
-            return array;
-        }
-
-        public bool Equals(SpanLike<T> other)
-        {
-            if (Length != other.Length)
-            {
-                return false;
-            }
-
-            var end = Length;
-            for (int i = 0; i < end; ++i)
-            {
-                if (!this[i].Equals(other[i]))
-                {
-                    return false;
-                }
-            }
-
-            return true;
-        }
-
-        public IEnumerator<T> GetEnumerator()
-        {
-            for (int i = 0; i < Length; ++i)
-            {
-                yield return this[i];
-            }
-        }
-
-        IEnumerator IEnumerable.GetEnumerator()
-        {
-            return (IEnumerator)GetEnumerator();
-        }
-    }
-
-    public static class SpanLike
-    {
-        struct GetSet<T> where T : struct
-        {
-            public SpanLike<T>.Getter Getter;
-            public SpanLike<T>.Setter Setter;
-        }
-
-        public static readonly Dictionary<Type, object> Map = new Dictionary<Type, object>()
-        {
-            {typeof(Byte), new GetSet<byte>{
-                Getter = (array, start) => array[start],
-                Setter = BitWriter.Write}},
-            {typeof(UInt16), new GetSet<UInt16>{
-                Getter = BitConverter.ToUInt16,
-                Setter = BitWriter.Write}},
-            {typeof(UInt32), new GetSet<UInt32>{
-                Getter = BitConverter.ToUInt32,
-                Setter = BitWriter.Write}},
-            {typeof(Int32), new GetSet<Int32>{
-                Getter = BitConverter.ToInt32,
-                Setter = BitWriter.Write}},
-            {typeof(Single), new GetSet<Single>{
-                Getter = BitConverter.ToSingle,
-                Setter = BitWriter.Write}},
-            {typeof(System.Numerics.Vector2), new GetSet<System.Numerics.Vector2>{
-                Getter = (array, start) =>
-                    new System.Numerics.Vector2(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(System.Numerics.Vector3), new GetSet<System.Numerics.Vector3>{
-                Getter = (array, start) =>
-                    new System.Numerics.Vector3(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(System.Numerics.Vector4), new GetSet<System.Numerics.Vector4>{
-                Getter = (array, start) =>
-                    new System.Numerics.Vector4(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8),
-                        BitConverter.ToSingle(array, start + 12)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(System.Numerics.Quaternion), new GetSet<System.Numerics.Quaternion>{
-                Getter = (array, start) =>
-                    new System.Numerics.Quaternion(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8),
-                        BitConverter.ToSingle(array, start + 12)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(System.Numerics.Matrix4x4), new GetSet<System.Numerics.Matrix4x4>{
-                Getter = (array, start) =>
-                    new System.Numerics.Matrix4x4(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8),
-                        BitConverter.ToSingle(array, start + 12),
-                        BitConverter.ToSingle(array, start + 16),
-                        BitConverter.ToSingle(array, start + 20),
-                        BitConverter.ToSingle(array, start + 24),
-                        BitConverter.ToSingle(array, start + 28),
-                        BitConverter.ToSingle(array, start + 32),
-                        BitConverter.ToSingle(array, start + 36),
-                        BitConverter.ToSingle(array, start + 40),
-                        BitConverter.ToSingle(array, start + 44),
-                        BitConverter.ToSingle(array, start + 48),
-                        BitConverter.ToSingle(array, start + 52),
-                        BitConverter.ToSingle(array, start + 56),
-                        BitConverter.ToSingle(array, start + 60)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(Byte4), new GetSet<Byte4>{
-                Getter = (array, start) =>
-                    new Byte4(
-                        array[start],
-                        array[start + 1],
-                        array[start + 2],
-                        array[start + 3]
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(UShort4), new GetSet<UShort4>{
-                Getter = (array, start) =>
-                    new UShort4(
-                        BitConverter.ToUInt16(array, start),
-                        BitConverter.ToUInt16(array, start + 2),
-                        BitConverter.ToUInt16(array, start + 4),
-                        BitConverter.ToUInt16(array, start + 6)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(SkinJoints), new GetSet<SkinJoints>{
-                Getter = (array, start) =>
-                    new SkinJoints
-                    {
-                        Joint0 = BitConverter.ToUInt16(array, start),
-                        Joint1 = BitConverter.ToUInt16(array, start + 2),
-                        Joint2 = BitConverter.ToUInt16(array, start + 4),
-                        Joint3 = BitConverter.ToUInt16(array, start + 6),
-                    },
-                Setter = BitWriter.Write
-            }},
-            {typeof(UnityEngine.Vector2), new GetSet<UnityEngine.Vector2>{
-                Getter = (array, start) =>
-                    new UnityEngine.Vector2(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(UnityEngine.Vector3), new GetSet<UnityEngine.Vector3>{
-                Getter = (array, start) =>
-                    new UnityEngine.Vector3(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(UnityEngine.Vector4), new GetSet<UnityEngine.Vector4>{
-                Getter = (array, start) =>
-                    new UnityEngine.Vector4(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8),
-                        BitConverter.ToSingle(array, start + 12)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {typeof(UnityEngine.Color), new GetSet<UnityEngine.Color>{
-                Getter = (array, start) =>
-                    new UnityEngine.Color(
-                        BitConverter.ToSingle(array, start),
-                        BitConverter.ToSingle(array, start + 4),
-                        BitConverter.ToSingle(array, start + 8),
-                        BitConverter.ToSingle(array, start + 12)
-                    ),
-                Setter = BitWriter.Write
-            }},
-            {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),
-                        BitConverter.ToSingle(array, start + 32),
-                        BitConverter.ToSingle(array, start + 48)),
-                        new UnityEngine.Vector4(BitConverter.ToSingle(array, start+4),
-                        BitConverter.ToSingle(array, start + 16+4),
-                        BitConverter.ToSingle(array, start + 32+4),
-                        BitConverter.ToSingle(array, start + 48+4)),
-                        new UnityEngine.Vector4(BitConverter.ToSingle(array, start+8),
-                        BitConverter.ToSingle(array, start + 16+8),
-                        BitConverter.ToSingle(array, start + 32+8),
-                        BitConverter.ToSingle(array, start + 48+8)),
-                        new UnityEngine.Vector4(BitConverter.ToSingle(array, start+12),
-                        BitConverter.ToSingle(array, start + 16+12),
-                        BitConverter.ToSingle(array, start + 32+12),
-                        BitConverter.ToSingle(array, start + 48+12))
-                    ),
-                Setter = BitWriter.Write
-            }},
-
-        };
-
-        public static SpanLike<T> Wrap<T>(ArraySegment<byte> bytes) where T : struct
-        {
-            if (!Map.TryGetValue(typeof(T), out object value))
-            {
-                throw new KeyNotFoundException($"{typeof(T)}");
-            }
-            var getset = (GetSet<T>)value;
-            return new SpanLike<T>(bytes, Marshal.SizeOf<T>(), getset.Getter, getset.Setter);
-        }
-
-        public static SpanLike<T> Create<T>(int itemCount) where T : struct
-        {
-            var itemSize = Marshal.SizeOf<T>();
-            var array = new byte[itemCount * itemSize];
-            return Wrap<T>(new ArraySegment<byte>(array));
-        }
-
-        public static SpanLike<T> CopyFrom<T>(T[] src) where T : struct
-        {
-            var buffer = new byte[src.Length * Marshal.SizeOf<T>()];
-            src.ToBytes(new ArraySegment<byte>(buffer));
-            return Wrap<T>(new ArraySegment<byte>(buffer));
-        }
-    }
-}
diff --git a/Assets/UniGLTF/Tests/UniGLTF/NumericTests.cs b/Assets/UniGLTF/Tests/UniGLTF/NumericTests.cs
index 8f75a5c93..05d0c8266 100644
--- a/Assets/UniGLTF/Tests/UniGLTF/NumericTests.cs
+++ b/Assets/UniGLTF/Tests/UniGLTF/NumericTests.cs
@@ -19,27 +19,6 @@ namespace UniGLTF
             Assert.AreEqual(orgAngle, angle);
         }
 
-        [Test]
-        [Category("Numerics")]
-        public void Vector4Test()
-        {
-            var bytes = new byte[4 * 4];
-            {
-                var span = SpanLike.Wrap<Single>(new ArraySegment<byte>(bytes));
-                span[0] = 1.0f;
-            }
-
-            {
-                var span = SpanLike.Wrap<Vector4>(new ArraySegment<byte>(bytes));
-                Assert.AreEqual(1.0f, span[0].X);
-            }
-
-            {
-                var span = SpanLike.Wrap<Quaternion>(new ArraySegment<byte>(bytes));
-                Assert.AreEqual(1.0f, span[0].X);
-            }
-        }
-
         [Test]
         [Category("Numerics")]
         public void Vector3Test()
diff --git a/Assets/UniGLTF/Tests/UniGLTF/SpanLikeTests.cs b/Assets/UniGLTF/Tests/UniGLTF/SpanLikeTests.cs
deleted file mode 100644
index 472201b06..000000000
--- a/Assets/UniGLTF/Tests/UniGLTF/SpanLikeTests.cs
+++ /dev/null
@@ -1,41 +0,0 @@
-using System;
-using NUnit.Framework;
-
-namespace UniGLTF
-{
-    public class SpanLikeTests
-    {
-        [Test]
-        [Category("SpanLike")]
-        public void CopyTest()
-        {
-            var src = new int[] { 255 };
-            var dst = new byte[4];
-
-            src.ToBytes(new ArraySegment<byte>(dst));
-
-            Assert.AreEqual(0xFF, dst[0]);
-            Assert.AreEqual(0, dst[1]);
-            Assert.AreEqual(0, dst[2]);
-            Assert.AreEqual(0, dst[3]);
-        }
-
-        [Test]
-        [Category("SpanLike")]
-        public void SpanLikeTest()
-        {
-            var v0 = new UnityEngine.Vector3(1, 2, 3);
-            var v1 = new UnityEngine.Vector3(4, 5, 6);
-            var positions = new UnityEngine.Vector3[]
-            {
-                v0,
-                v1,
-            };
-            var span = SpanLike.CopyFrom(positions);
-
-            Assert.AreEqual(2, span.Length);
-            Assert.AreEqual(v0, span[0]);
-            Assert.AreEqual(v1, span[1]);
-        }
-    }
-}
diff --git a/Assets/UniGLTF/Tests/UniGLTF/SpanLikeTests.cs.meta b/Assets/UniGLTF/Tests/UniGLTF/SpanLikeTests.cs.meta
deleted file mode 100644
index b3756ed6d..000000000
--- a/Assets/UniGLTF/Tests/UniGLTF/SpanLikeTests.cs.meta
+++ /dev/null
@@ -1,11 +0,0 @@
-fileFormatVersion: 2
-guid: f70b7312ba0d32b4493231c6f8a42e4c
-MonoImporter:
-  externalObjects: {}
-  serializedVersion: 2
-  defaultReferences: []
-  executionOrder: 0
-  icon: {instanceID: 0}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: 
diff --git a/Assets/VRM10/Runtime/IO/Model/MeshWriter.cs b/Assets/VRM10/Runtime/IO/Model/MeshWriter.cs
index d63bba48d..7a7ef16f7 100644
--- a/Assets/VRM10/Runtime/IO/Model/MeshWriter.cs
+++ b/Assets/VRM10/Runtime/IO/Model/MeshWriter.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Numerics;
 using UniGLTF;
 using Unity.Collections;
 using VrmLib;
@@ -13,48 +12,6 @@ namespace UniVRM10
     /// </summary>
     public static class MeshWriter
     {
-        static void Vec3MinMax(ArraySegment<byte> bytes, glTFAccessor accessor)
-        {
-            var positions = SpanLike.Wrap<Vector3>(bytes);
-            var min = new Vector3(float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity);
-            var max = new Vector3(float.NegativeInfinity, float.NegativeInfinity, float.NegativeInfinity);
-            foreach (var p in positions)
-            {
-                min = Vector3.Min(min, p);
-                max = Vector3.Max(max, p);
-            }
-            accessor.min = min.ToFloat3();
-            accessor.max = max.ToFloat3();
-        }
-
-        // static int ExportIndices(ExportingGltfData data, BufferAccessor x, int offset, int count, ExportArgs option)
-        // {
-        //     if (x.Count <= ushort.MaxValue)
-        //     {
-        //         if (x.ComponentType == AccessorValueType.UNSIGNED_INT)
-        //         {
-        //             // ensure ushort
-        //             var src = x.GetSpan<UInt32>().Slice(offset, count);
-        //             var bytes = new byte[src.Length * 2];
-        //             var dst = SpanLike.Wrap<UInt16>(new ArraySegment<byte>(bytes));
-        //             for (int i = 0; i < src.Length; ++i)
-        //             {
-        //                 dst[i] = (ushort)src[i];
-        //             }
-        //             var accessor = new BufferAccessor(new ArraySegment<byte>(bytes), AccessorValueType.UNSIGNED_SHORT, AccessorVectorType.SCALAR, count);
-        //             return accessor.AddAccessorTo(data, 0, option.sparse, null, 0, count);
-        //         }
-        //         else
-        //         {
-        //             return x.AddAccessorTo(data, 0, option.sparse, null, offset, count);
-        //         }
-        //     }
-        //     else
-        //     {
-        //         return x.AddAccessorTo(data, 0, option.sparse, null, offset, count);
-        //     }
-        // }
-
         /// <summary>
         /// https://github.com/vrm-c/UniVRM/issues/800
         ///
@@ -67,7 +24,7 @@ namespace UniVRM10
         /// <param name="gltfMesh"></param>
         /// <param name="option"></param>
         static IEnumerable<glTFPrimitives> ExportMeshDivided(this VrmLib.Mesh mesh, List<object> materials,
-            ExportingGltfData  writer, ExportArgs option)
+            ExportingGltfData writer, ExportArgs option)
         {
             var usedIndices = new List<int>();
             var meshIndices = mesh.IndexBuffer.GetAsIntArray();
@@ -161,7 +118,7 @@ namespace UniVRM10
         /// <param name="data"></param>
         /// <param name="option"></param>
         /// <returns></returns>
-        public static glTFMesh ExportMeshGroup(this MeshGroup src, List<object> materials, ExportingGltfData  writer, ExportArgs option)
+        public static glTFMesh ExportMeshGroup(this MeshGroup src, List<object> materials, ExportingGltfData writer, ExportArgs option)
         {
             var gltfMesh = new glTFMesh
             {
diff --git a/Assets/VRM10/Runtime/Migration/MigrationVrm.cs b/Assets/VRM10/Runtime/Migration/MigrationVrm.cs
index c14d85281..6311ccb2f 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationVrm.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationVrm.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using UniGLTF;
 using UniJSON;
+using Unity.Collections;
 
 namespace UniVRM10
 {
@@ -18,7 +19,7 @@ namespace UniVRM10
             }
         }
 
-        static (int, int) GetVertexRange(SpanLike<int> indices)
+        static (int, int) GetVertexRange(NativeArray<int> indices)
         {
             var min = int.MaxValue; ;
             var max = 0;