diff --git a/Optuna/Storage/IStorage.cs b/Optuna/Storage/IOptunaStorage.cs
similarity index 98%
rename from Optuna/Storage/IStorage.cs
rename to Optuna/Storage/IOptunaStorage.cs
index 93ee838b..81cc8ecf 100644
--- a/Optuna/Storage/IStorage.cs
+++ b/Optuna/Storage/IOptunaStorage.cs
@@ -5,7 +5,7 @@
 
 namespace Optuna.Storage
 {
-    public interface IStorage
+    public interface IOptunaStorage
     {
         // Basic study manipulation
         int CreateNewStudy(StudyDirection[] studyDirections, string studyName);
diff --git a/Optuna/Storage/Journal/Storage.cs b/Optuna/Storage/Journal/Storage.cs
index d5d4b3b1..65dea23f 100644
--- a/Optuna/Storage/Journal/Storage.cs
+++ b/Optuna/Storage/Journal/Storage.cs
@@ -10,7 +10,7 @@
 
 namespace Optuna.Storage.Journal
 {
-    public class JournalStorage : IStorage
+    public class JournalStorage : IOptunaStorage
     {
         private readonly Dictionary<int, Study.Study> _studies = new Dictionary<int, Study.Study>();
         private int _nextStudyId;
diff --git a/Optuna/Storage/RDB/Storage.cs b/Optuna/Storage/RDB/Storage.cs
index 374f679d..8981592a 100644
--- a/Optuna/Storage/RDB/Storage.cs
+++ b/Optuna/Storage/RDB/Storage.cs
@@ -12,7 +12,7 @@
 
 namespace Optuna.Storage.RDB
 {
-    public class SqliteStorage : IStorage
+    public class SqliteStorage : IOptunaStorage
     {
         private readonly Dictionary<int, Study.Study> _studies = new Dictionary<int, Study.Study>();
         private readonly SQLiteConnectionStringBuilder _sqliteConnection;
diff --git a/Optuna/Study/Study.cs b/Optuna/Study/Study.cs
index 520af27c..f2293749 100644
--- a/Optuna/Study/Study.cs
+++ b/Optuna/Study/Study.cs
@@ -18,9 +18,9 @@ public class Study
         public int StudyId { get; }
 
         private readonly bool _isMultiObjective;
-        private readonly IStorage _storage;
+        private readonly IOptunaStorage _storage;
 
-        public Study(IStorage storage, int studyID, string studyName, StudyDirection[] directions)
+        public Study(IOptunaStorage storage, int studyID, string studyName, StudyDirection[] directions)
         {
             StudyId = studyID;
             _storage = storage;
@@ -95,7 +95,7 @@ private Trial.Trial[] GetBestTrials()
             return MultiObjective.GetParetoFrontTrials(Trials, Directions);
         }
 
-        public static StudySummary[] GetAllStudySummaries(IStorage storage)
+        public static StudySummary[] GetAllStudySummaries(IOptunaStorage storage)
         {
             Study[] studies = storage.GetAllStudies();
             var studySummaries = new StudySummary[studies.Length];
diff --git a/OptunaTests/Storage/StorageSameBevaviorTests.cs b/OptunaTests/Storage/StorageSameBevaviorTests.cs
index f157255b..dbd79631 100644
--- a/OptunaTests/Storage/StorageSameBevaviorTests.cs
+++ b/OptunaTests/Storage/StorageSameBevaviorTests.cs
@@ -12,7 +12,7 @@ public class StorageSameBehaviorTests
         [InlineData(@"TestFile/journal.log", "log")]
         public void StorageLoadTest(string path, string type)
         {
-            IStorage storage;
+            IOptunaStorage storage;
             int offset = 0; // journal starts from 0
 
             if (type == "sqlite")
diff --git a/Tunny.Core/Settings/Storage.cs b/Tunny.Core/Settings/Storage.cs
index 455bc5a7..ea7fece1 100644
--- a/Tunny.Core/Settings/Storage.cs
+++ b/Tunny.Core/Settings/Storage.cs
@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 
+using Optuna.Storage;
 using Optuna.Study;
 
 using Python.Runtime;
@@ -131,7 +132,7 @@ private dynamic CreateArtifactBackendProcess()
         public Study[] GetAllStudies()
         {
             TLog.MethodStart();
-            Optuna.Storage.IStorage storage;
+            IOptunaStorage storage;
             switch (Type)
             {
                 case StorageType.Sqlite: