diff --git a/src/LibHac/Diag/Assert.cs b/src/LibHac/Diag/Assert.cs
index 318502da..4c22a26a 100644
--- a/src/LibHac/Diag/Assert.cs
+++ b/src/LibHac/Diag/Assert.cs
@@ -2,6 +2,7 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
+using LibHac.Common;
 using LibHac.Diag.Impl;
 using LibHac.Os;
 
@@ -395,6 +396,98 @@ public static class Assert
         NotNullImpl(AssertionType.SdkRequires, value, valueText, functionName, fileName, lineNumber);
     }
 
+    // ---------------------------------------------------------------------
+    // Not null UniqueRef<T>
+    // ---------------------------------------------------------------------
+
+    private static void NotNullImpl<T>(AssertionType assertionType, in UniqueRef<T> value,
+        string valueText, string functionName, string fileName, int lineNumber) where T : class, IDisposable
+    {
+        if (AssertImpl.NotNull(in value))
+            return;
+
+        AssertImpl.InvokeAssertionNotNull(assertionType, valueText, functionName, fileName, lineNumber);
+    }
+
+    [Conditional(AssertCondition)]
+    public static void NotNull<T>(in UniqueRef<T> value,
+        [CallerArgumentExpression("value")] string valueText = "",
+        [CallerMemberName] string functionName = "",
+        [CallerFilePath] string fileName = "",
+        [CallerLineNumber] int lineNumber = 0)
+        where T : class, IDisposable
+    {
+        NotNullImpl(AssertionType.UserAssert, in value, valueText, functionName, fileName, lineNumber);
+    }
+
+    [Conditional(AssertCondition)]
+    internal static void SdkNotNull<T>(in UniqueRef<T> value,
+        [CallerArgumentExpression("value")] string valueText = "",
+        [CallerMemberName] string functionName = "",
+        [CallerFilePath] string fileName = "",
+        [CallerLineNumber] int lineNumber = 0)
+        where T : class, IDisposable
+    {
+        NotNullImpl(AssertionType.SdkAssert, in value, valueText, functionName, fileName, lineNumber);
+    }
+
+    [Conditional(AssertCondition)]
+    internal static void SdkRequiresNotNull<T>(in UniqueRef<T> value,
+        [CallerArgumentExpression("value")] string valueText = "",
+        [CallerMemberName] string functionName = "",
+        [CallerFilePath] string fileName = "",
+        [CallerLineNumber] int lineNumber = 0)
+        where T : class, IDisposable
+    {
+        NotNullImpl(AssertionType.SdkRequires, in value, valueText, functionName, fileName, lineNumber);
+    }
+
+    // ---------------------------------------------------------------------
+    // Not null SharedRef<T>
+    // ---------------------------------------------------------------------
+
+    private static void NotNullImpl<T>(AssertionType assertionType, in SharedRef<T> value,
+        string valueText, string functionName, string fileName, int lineNumber) where T : class, IDisposable
+    {
+        if (AssertImpl.NotNull(in value))
+            return;
+
+        AssertImpl.InvokeAssertionNotNull(assertionType, valueText, functionName, fileName, lineNumber);
+    }
+
+    [Conditional(AssertCondition)]
+    public static void NotNull<T>(in SharedRef<T> value,
+        [CallerArgumentExpression("value")] string valueText = "",
+        [CallerMemberName] string functionName = "",
+        [CallerFilePath] string fileName = "",
+        [CallerLineNumber] int lineNumber = 0)
+        where T : class, IDisposable
+    {
+        NotNullImpl(AssertionType.UserAssert, in value, valueText, functionName, fileName, lineNumber);
+    }
+
+    [Conditional(AssertCondition)]
+    internal static void SdkNotNull<T>(in SharedRef<T> value,
+        [CallerArgumentExpression("value")] string valueText = "",
+        [CallerMemberName] string functionName = "",
+        [CallerFilePath] string fileName = "",
+        [CallerLineNumber] int lineNumber = 0)
+        where T : class, IDisposable
+    {
+        NotNullImpl(AssertionType.SdkAssert, in value, valueText, functionName, fileName, lineNumber);
+    }
+
+    [Conditional(AssertCondition)]
+    internal static void SdkRequiresNotNull<T>(in SharedRef<T> value,
+        [CallerArgumentExpression("value")] string valueText = "",
+        [CallerMemberName] string functionName = "",
+        [CallerFilePath] string fileName = "",
+        [CallerLineNumber] int lineNumber = 0)
+        where T : class, IDisposable
+    {
+        NotNullImpl(AssertionType.SdkRequires, in value, valueText, functionName, fileName, lineNumber);
+    }
+
     // ---------------------------------------------------------------------
     // Null
     // ---------------------------------------------------------------------
diff --git a/src/LibHac/Diag/Impl/AssertImpl.cs b/src/LibHac/Diag/Impl/AssertImpl.cs
index 63ce1c12..cc16becc 100644
--- a/src/LibHac/Diag/Impl/AssertImpl.cs
+++ b/src/LibHac/Diag/Impl/AssertImpl.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using LibHac.Common;
 using LibHac.Util;
 
 namespace LibHac.Diag.Impl;
@@ -145,6 +146,16 @@ internal static class AssertImpl
         return !Unsafe.IsNullRef(ref MemoryMarshal.GetReference(span)) || span.Length == 0;
     }
 
+    public static bool NotNull<T>(in UniqueRef<T> item) where T : class, IDisposable
+    {
+        return item.HasValue;
+    }
+
+    public static bool NotNull<T>(in SharedRef<T> item) where T : class, IDisposable
+    {
+        return item.HasValue;
+    }
+
     public static bool WithinRange(int value, int lowerInclusive, int upperExclusive)
     {
         return lowerInclusive <= value && value < upperExclusive;
diff --git a/src/LibHac/Fs/SubStorage.cs b/src/LibHac/Fs/SubStorage.cs
index 115d4a4b..7cd86327 100644
--- a/src/LibHac/Fs/SubStorage.cs
+++ b/src/LibHac/Fs/SubStorage.cs
@@ -201,6 +201,7 @@ public class SubStorage : IStorage
         if (rc.IsFailure()) return rc;
 
         _size = size;
+
         return Result.Success;
     }
 
@@ -217,9 +218,13 @@ public class SubStorage : IStorage
     protected override Result DoOperateRange(Span<byte> outBuffer, OperationId operationId, long offset, long size, ReadOnlySpan<byte> inBuffer)
     {
         if (!IsValid()) return ResultFs.NotInitialized.Log();
-        if (size == 0) return Result.Success;
-        if (!CheckOffsetAndSize(_offset, size)) return ResultFs.OutOfRange.Log();
 
-        return base.DoOperateRange(outBuffer, operationId, _offset + offset, size, inBuffer);
+        if (operationId != OperationId.InvalidateCache)
+        {
+            if (size == 0) return Result.Success;
+            if (!CheckOffsetAndSize(_offset, size)) return ResultFs.OutOfRange.Log();
+        }
+
+        return BaseStorage.OperateRange(outBuffer, operationId, _offset + offset, size, inBuffer);
     }
 }
diff --git a/src/LibHac/Fs/ValueSubStorage.cs b/src/LibHac/Fs/ValueSubStorage.cs
new file mode 100644
index 00000000..1a03624f
--- /dev/null
+++ b/src/LibHac/Fs/ValueSubStorage.cs
@@ -0,0 +1,179 @@
+using System;
+using System.Runtime.CompilerServices;
+using LibHac.Common;
+using LibHac.Diag;
+
+namespace LibHac.Fs;
+
+[NonCopyableDisposable]
+public struct ValueSubStorage : IDisposable
+{
+    private IStorage _baseStorage;
+    private long _offset;
+    private long _size;
+    private bool _isResizable;
+    private SharedRef<IStorage> _sharedBaseStorage;
+
+    public ValueSubStorage()
+    {
+        _baseStorage = null;
+        _offset = 0;
+        _size = 0;
+        _isResizable = false;
+        _sharedBaseStorage = new SharedRef<IStorage>();
+    }
+
+    public ValueSubStorage(in ValueSubStorage other)
+    {
+        _baseStorage = other._baseStorage;
+        _offset = other._offset;
+        _size = other._size;
+        _isResizable = other._isResizable;
+        _sharedBaseStorage = SharedRef<IStorage>.CreateCopy(in other._sharedBaseStorage);
+    }
+
+    public ValueSubStorage(IStorage baseStorage, long offset, long size)
+    {
+        _baseStorage = baseStorage;
+        _offset = offset;
+        _size = size;
+        _isResizable = false;
+        _sharedBaseStorage = new SharedRef<IStorage>();
+
+        Assert.SdkRequiresNotNull(baseStorage);
+        Assert.SdkRequiresLessEqual(0, offset);
+        Assert.SdkRequiresLessEqual(0, size);
+    }
+
+    public ValueSubStorage(in ValueSubStorage subStorage, long offset, long size)
+    {
+        _baseStorage = subStorage._baseStorage;
+        _offset = subStorage._offset + offset;
+        _size = size;
+        _isResizable = false;
+        _sharedBaseStorage = SharedRef<IStorage>.CreateCopy(in subStorage._sharedBaseStorage);
+
+        Assert.SdkRequiresLessEqual(0, offset);
+        Assert.SdkRequiresLessEqual(0, size);
+        Assert.SdkRequires(subStorage.IsValid());
+        Assert.SdkRequiresGreaterEqual(subStorage._size, offset + size);
+    }
+
+    public ValueSubStorage(in SharedRef<IStorage> baseStorage, long offset, long size)
+    {
+        _baseStorage = baseStorage.Get;
+        _offset = offset;
+        _size = size;
+        _isResizable = false;
+        _sharedBaseStorage = SharedRef<IStorage>.CreateCopy(in baseStorage);
+
+        Assert.SdkRequiresNotNull(in baseStorage);
+        Assert.SdkRequiresLessEqual(0, _offset);
+        Assert.SdkRequiresLessEqual(0, _size);
+    }
+
+    public void Dispose()
+    {
+        _baseStorage = null;
+        _sharedBaseStorage.Destroy();
+    }
+
+    public void Set(in ValueSubStorage other)
+    {
+        if (!Unsafe.AreSame(ref Unsafe.AsRef(in this), ref Unsafe.AsRef(in other)))
+        {
+            _baseStorage = other._baseStorage;
+            _offset = other._offset;
+            _size = other._size;
+            _isResizable = other._isResizable;
+            _sharedBaseStorage.SetByCopy(in other._sharedBaseStorage);
+        }
+    }
+
+    private readonly bool IsValid() => _baseStorage is not null;
+
+    public void SetResizable(bool isResizable)
+    {
+        _isResizable = isResizable;
+    }
+
+    public readonly Result Read(long offset, Span<byte> destination)
+    {
+        if (!IsValid()) return ResultFs.NotInitialized.Log();
+        if (destination.Length == 0) return Result.Success;
+
+        if (!IStorage.CheckAccessRange(offset, destination.Length, _size))
+            return ResultFs.OutOfRange.Log();
+
+        return _baseStorage.Read(_offset + offset, destination);
+    }
+
+    public readonly Result Write(long offset, ReadOnlySpan<byte> source)
+    {
+        if (!IsValid()) return ResultFs.NotInitialized.Log();
+        if (source.Length == 0) return Result.Success;
+
+        if (!IStorage.CheckAccessRange(offset, source.Length, _size))
+            return ResultFs.OutOfRange.Log();
+
+        return _baseStorage.Write(_offset + offset, source);
+    }
+
+    public readonly Result Flush()
+    {
+        if (!IsValid()) return ResultFs.NotInitialized.Log();
+
+        return _baseStorage.Flush();
+    }
+
+    public Result SetSize(long size)
+    {
+        if (!IsValid()) return ResultFs.NotInitialized.Log();
+        if (!_isResizable) return ResultFs.UnsupportedSetSizeForNotResizableSubStorage.Log();
+        if (!IStorage.CheckOffsetAndSize(_offset, size)) return ResultFs.InvalidSize.Log();
+
+        Result rc = _baseStorage.GetSize(out long currentSize);
+        if (rc.IsFailure()) return rc;
+
+        if (currentSize != _offset + _size)
+        {
+            // SubStorage cannot be resized unless it is located at the end of the base storage.
+            return ResultFs.UnsupportedSetSizeForResizableSubStorage.Log();
+        }
+
+        rc = _baseStorage.SetSize(_offset + size);
+        if (rc.IsFailure()) return rc;
+
+        _size = size;
+
+        return Result.Success;
+    }
+
+    public readonly Result GetSize(out long size)
+    {
+        UnsafeHelpers.SkipParamInit(out size);
+
+        if (!IsValid()) return ResultFs.NotInitialized.Log();
+
+        size = _size;
+        return Result.Success;
+    }
+
+    public readonly Result OperateRange(OperationId operationId, long offset, long size)
+    {
+        return OperateRange(Span<byte>.Empty, operationId, offset, size, ReadOnlySpan<byte>.Empty);
+    }
+
+    public readonly Result OperateRange(Span<byte> outBuffer, OperationId operationId, long offset, long size, ReadOnlySpan<byte> inBuffer)
+    {
+        if (!IsValid()) return ResultFs.NotInitialized.Log();
+
+        if (operationId != OperationId.InvalidateCache)
+        {
+            if (size == 0) return Result.Success;
+            if (!IStorage.CheckOffsetAndSize(_offset, size)) return ResultFs.OutOfRange.Log();
+        }
+
+        return _baseStorage.OperateRange(outBuffer, operationId, _offset + offset, size, inBuffer);
+    }
+}