diff --git a/Assets/VRM10/Runtime/Components/Expression/ExpressionKey.cs b/Assets/VRM10/Runtime/Components/Expression/ExpressionKey.cs
index a79b69279..c329bee70 100644
--- a/Assets/VRM10/Runtime/Components/Expression/ExpressionKey.cs
+++ b/Assets/VRM10/Runtime/Components/Expression/ExpressionKey.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using UniGLTF;
 using VRMShaders;
 
 namespace UniVRM10
@@ -31,9 +30,9 @@ namespace UniVRM10
         public readonly string Name;
 
         /// <summary>
-        /// Id for comparison of ExpressionKey.
+        /// Key's hashcode for comparison.
         /// </summary>
-        private readonly string _id;
+        private readonly int _hashCode;
 
         public bool IsBlink
         {
@@ -93,12 +92,14 @@ namespace UniVRM10
             {
                 if (PresetNameDictionary.ContainsKey((Preset)))
                 {
-                    _id = Name = PresetNameDictionary[Preset];
+                    Name = PresetNameDictionary[Preset];
+                    _hashCode = Name.GetHashCode();
                 }
                 else
                 {
                     PresetNameDictionary.Add(Preset, Preset.ToString());
-                    _id = Name = PresetNameDictionary[Preset];
+                    Name = PresetNameDictionary[Preset];
+                    _hashCode = Name.GetHashCode();
                 }
             }
             else
@@ -108,8 +109,8 @@ namespace UniVRM10
                     throw new ArgumentException("name is required for ExpressionPreset.Custom");
                 }
 
-                _id = $"{UnknownPresetPrefix}{customName}";
                 Name = customName;
+                _hashCode = $"{UnknownPresetPrefix}{customName}".GetHashCode();
             }
         }
 
@@ -145,19 +146,24 @@ namespace UniVRM10
 
         public override string ToString()
         {
-            return _id.Replace(UnknownPresetPrefix, "");
+            return Name;
         }
 
         public bool Equals(ExpressionKey other)
         {
-            return _id == other._id;
+            // Early pruning
+            if (_hashCode != other._hashCode) return false;
+
+            if (Preset != other.Preset) return false;
+            if (Preset != ExpressionPreset.custom) return true;
+            return Name == other.Name;
         }
 
         public override bool Equals(object obj)
         {
-            if (obj is ExpressionKey)
+            if (obj is ExpressionKey key)
             {
-                return Equals((ExpressionKey)obj);
+                return Equals(key);
             }
             else
             {
@@ -167,14 +173,9 @@ namespace UniVRM10
 
         public override int GetHashCode()
         {
-            return _id.GetHashCode();
+            return _hashCode;
         }
 
-        // public bool Match(VRM10Expression clip)
-        // {
-        //     return this.Equals(CreateFromClip(clip));
-        // }
-
         public int CompareTo(ExpressionKey other)
         {
             if (Preset != other.Preset)
@@ -192,5 +193,25 @@ namespace UniVRM10
                 return new SubAssetKey(typeof(VRM10Expression), this.ToString());
             }
         }
+
+        public static EqualityComparer Comparer { get; } = new();
+
+        public sealed class EqualityComparer : IEqualityComparer<ExpressionKey>
+        {
+            internal EqualityComparer()
+            {
+
+            }
+
+            public bool Equals(ExpressionKey x, ExpressionKey y)
+            {
+                return x.Equals(y);
+            }
+
+            public int GetHashCode(ExpressionKey obj)
+            {
+                return obj.GetHashCode();
+            }
+        }
     }
 }
diff --git a/Assets/VRM10/Runtime/Components/Expression/ExpressionMerger.cs b/Assets/VRM10/Runtime/Components/Expression/ExpressionMerger.cs
index b8ec76ec4..64fb82b0d 100644
--- a/Assets/VRM10/Runtime/Components/Expression/ExpressionMerger.cs
+++ b/Assets/VRM10/Runtime/Components/Expression/ExpressionMerger.cs
@@ -28,10 +28,12 @@ namespace UniVRM10
 
         public ExpressionMerger(VRM10ObjectExpression expressions, Transform root)
         {
-            m_clipMap = expressions.Clips.ToDictionary(x => expressions.CreateKey(x.Clip), x => x.Clip);
-
-            m_valueMap = new Dictionary<ExpressionKey, float>();
-
+            m_clipMap = expressions.Clips.ToDictionary(
+                x => expressions.CreateKey(x.Clip),
+                x => x.Clip,
+                ExpressionKey.Comparer
+            );
+            m_valueMap = new Dictionary<ExpressionKey, float>(ExpressionKey.Comparer);
             m_morphTargetBindingMerger = new MorphTargetBindingMerger(m_clipMap, root);
             m_materialValueBindingMerger = new MaterialValueBindingMerger(m_clipMap, root);
         }
diff --git a/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeExpression.cs b/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeExpression.cs
index da3bc541f..4082f8b89 100644
--- a/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeExpression.cs
+++ b/Assets/VRM10/Runtime/Components/Vrm10Runtime/Vrm10RuntimeExpression.cs
@@ -31,15 +31,25 @@ namespace UniVRM10
             Restore();
 
             _merger = new ExpressionMerger(target.Vrm.Expression, target.transform);
-            _keys = target.Vrm.Expression.Clips.Select(x => target.Vrm.Expression.CreateKey(x.Clip)).ToList();
+            _keys = target.Vrm.Expression.Clips
+                .Select(x => target.Vrm.Expression.CreateKey(x.Clip))
+                .ToList();
             var oldInputWeights = _inputWeights;
-            _inputWeights = _keys.ToDictionary(x => x, x => 0f);
+            _inputWeights = _keys.ToDictionary(
+                x => x,
+                x => 0f,
+                ExpressionKey.Comparer
+            );
             foreach (var key in _keys)
             {
                 // remain user input weights.
                 if (oldInputWeights.ContainsKey(key)) _inputWeights[key] = oldInputWeights[key];
             }
-            _actualWeights = _keys.ToDictionary(x => x, x => 0f);
+            _actualWeights = _keys.ToDictionary(
+                x => x,
+                x => 0f,
+                ExpressionKey.Comparer
+            );
             _validator = ExpressionValidatorFactory.Create(target.Vrm.Expression);
             _eyeDirectionProvider = eyeDirectionProvider;
             _eyeDirectionApplicable = eyeDirectionApplicable;