diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.cpp b/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.cpp
index 0faa04fcd..d200ef4bc 100644
--- a/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.cpp
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.cpp
@@ -71,3 +71,98 @@ Result FsPathUtils::ConvertPathForServiceObject(FsPath *out, const char *path) {
     const size_t max_len = (FS_MAX_PATH-1) - prefix_len;
     return FsPathUtils::VerifyPath(out->str + prefix_len, max_len, max_len);
 }
+
+Result FsPathUtils::IsNormalized(bool *out, const char *path) {
+    /* Nintendo uses a state machine here. */
+    enum class PathState {
+        Start,
+        Normal,
+        FirstSeparator,
+        Separator,
+        CurrentDir,
+        ParentDir,
+        WindowsDriveLetter,
+    };
+    
+    PathState state = PathState::Start;
+    
+    for (const char *cur = path; *cur != 0; cur++) {
+        const char c = *cur;
+        switch (state) {
+            case PathState::Start:
+                if (IsWindowsDriveLetter(c)) {
+                    state = PathState::WindowsDriveLetter;
+                } else if (c == '/') {
+                    state = PathState::FirstSeparator;
+                } else {
+                    return ResultFsInvalidPathFormat;
+                }
+                break;
+            case PathState::Normal:
+                if (c == '/') {
+                    state = PathState::Separator;
+                }
+                break;
+            case PathState::FirstSeparator:
+            case PathState::Separator:
+                /* It is unclear why first separator and separator are separate states... */
+                if (c == '/') {
+                    *out = false;
+                    return 0;
+                } else if (c == '.') {
+                    state = PathState::CurrentDir;
+                } else {
+                    state = PathState::Normal;
+                }
+                break;
+            case PathState::CurrentDir:
+                if (c == '/') {
+                    *out = false;
+                    return 0;
+                } else if (c == '.') {
+                    state = PathState::ParentDir;
+                } else {
+                    state = PathState::Normal;
+                }
+                break;
+            case PathState::ParentDir:
+                if (c == '/') {
+                    *out = false;
+                    return 0;
+                } else {
+                    state = PathState::Normal;
+                }
+                break;
+            case PathState::WindowsDriveLetter:
+                if (c == ':') {
+                    *out = true;
+                    return 0;
+                } else {
+                    return ResultFsInvalidPathFormat;
+                }
+                break;
+        }
+    }
+    
+    switch (state) {
+        case PathState::Start:
+        case PathState::WindowsDriveLetter:
+            return ResultFsInvalidPathFormat;
+        case PathState::FirstSeparator:
+        case PathState::Separator:
+            *out = false;
+            break;
+        case PathState::Normal:
+        case PathState::CurrentDir:
+        case PathState::ParentDir:
+            *out = true;
+            break;
+    }
+    
+    return 0;
+}
+
+Result FsPathUtils::Normalize(char *out, size_t max_out_size, const char *src, size_t *out_size) {
+    /* TODO */
+    return ResultFsNotImplemented;
+}
diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.hpp b/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.hpp
index 975fe0337..fbd073c13 100644
--- a/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.hpp
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_path_utils.hpp
@@ -25,10 +25,16 @@ class FsPathUtils {
     public:
         static Result VerifyPath(const char *path, size_t max_path_len, size_t max_name_len);
         static Result ConvertPathForServiceObject(FsPath *out, const char *path);
+        
+        static Result IsNormalized(bool *out, const char *path);
+        static Result Normalize(char *out, size_t max_out_size, const char *src, size_t *out_size);
 
+        static bool IsWindowsDriveLetter(const char c) {
+            return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z');
+        }
+        
         static bool IsWindowsAbsolutePath(const char *path) {
             /* Nintendo uses this in path comparisons... */
-            return (('a' <= path[0] && path[0] <= 'z') || (('A' <= path[0] && path[0] <= 'Z'))) &&
-                    path[0] != 0 && path[1] == ':';
+            return IsWindowsDriveLetter(path[0]) && path[1] == ':';
         }
 };
diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_results.hpp b/stratosphere/ams_mitm/source/fs_mitm/fs_results.hpp
index 6efecd17d..9dd12dd60 100644
--- a/stratosphere/ams_mitm/source/fs_mitm/fs_results.hpp
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_results.hpp
@@ -22,10 +22,15 @@ static constexpr u32 Module_Fs = 2;
 static constexpr Result ResultFsNotImplemented       = MAKERESULT(Module_Fs, 3001);
 static constexpr Result ResultFsOutOfRange           = MAKERESULT(Module_Fs, 3005);
 
-static constexpr Result ResultFsInvalidArgument      = MAKERESULT(Module_Fs, 6001);
-static constexpr Result ResultFsInvalidPath          = MAKERESULT(Module_Fs, 6002);
-static constexpr Result ResultFsTooLongPath          = MAKERESULT(Module_Fs, 6003);
-static constexpr Result ResultFsInvalidCharacter     = MAKERESULT(Module_Fs, 6004);
+static constexpr Result ResultFsAllocationFailureInSubDirectoryFileSystem = MAKERESULT(Module_Fs, 3355);
+
+static constexpr Result ResultFsInvalidArgument       = MAKERESULT(Module_Fs, 6001);
+static constexpr Result ResultFsInvalidPath           = MAKERESULT(Module_Fs, 6002);
+static constexpr Result ResultFsTooLongPath           = MAKERESULT(Module_Fs, 6003);
+static constexpr Result ResultFsInvalidCharacter      = MAKERESULT(Module_Fs, 6004);
+static constexpr Result ResultFsInvalidPathFormat     = MAKERESULT(Module_Fs, 6005);
+static constexpr Result ResultFsDirectoryUnobtainable = MAKERESULT(Module_Fs, 6006);
+static constexpr Result ResultFsNotNormalized         = MAKERESULT(Module_Fs, 6007);
 
 static constexpr Result ResultFsInvalidOffset        = MAKERESULT(Module_Fs, 6061);
 static constexpr Result ResultFsInvalidSize          = MAKERESULT(Module_Fs, 6062);
diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_subdirectory_filesystem.cpp b/stratosphere/ams_mitm/source/fs_mitm/fs_subdirectory_filesystem.cpp
new file mode 100644
index 000000000..0b17a5e8c
--- /dev/null
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_subdirectory_filesystem.cpp
@@ -0,0 +1,248 @@
+/*
+ * Copyright (c) 2018 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <cstring>
+#include <switch.h>
+#include <stratosphere.hpp>
+
+#include "fs_subdirectory_filesystem.hpp"
+#include "fs_path_utils.hpp"
+
+Result SubDirectoryFileSystem::Initialize(const char *bp) {
+    if (strnlen(bp, FS_MAX_PATH) >= FS_MAX_PATH) {
+        return ResultFsTooLongPath;
+    }
+    
+    /* Normalize the path. */
+    char normal_path[FS_MAX_PATH + 1];
+    size_t normal_path_len;
+    Result rc = FsPathUtils::Normalize(normal_path, sizeof(normal_path), bp, &normal_path_len);
+    if (R_FAILED(rc)) {
+        /* N calls svcBreak here. */
+        std::abort();
+    }
+    
+    /* Ensure terminating '/' */
+    if (normal_path[normal_path_len-1] != '/') {
+        if (normal_path_len + 2 > sizeof(normal_path)) {
+            std::abort();
+        }
+        
+        strncat(normal_path, "/", 2);
+        normal_path[sizeof(normal_path)-1] = 0;
+        normal_path_len++;
+    }
+    
+    this->base_path_len = normal_path_len + 1;
+    this->base_path = reinterpret_cast<char *>(malloc(this->base_path_len));
+    if (this->base_path == nullptr) {
+        return ResultFsAllocationFailureInSubDirectoryFileSystem;
+    }
+    
+    std::strncpy(this->base_path, normal_path, this->base_path_len);
+    this->base_path[this->base_path_len-1] = 0;
+    return 0;
+}
+
+Result SubDirectoryFileSystem::GetFullPath(char *out, size_t out_size, const char *relative_path) {
+    if (this->base_path_len + strnlen(relative_path, FS_MAX_PATH) > out_size) {
+        return ResultFsTooLongPath;
+    }
+    
+    /* Copy base path. */
+    std::strncpy(out, this->base_path, out_size);
+    out[out_size-1] = 0;
+    
+    /* Normalize it. */
+    return FsPathUtils::Normalize(out + this->base_path_len - 2, out_size - (this->base_path_len - 2), relative_path, nullptr);
+}
+
+Result SubDirectoryFileSystem::CreateFileImpl(FsPath &path, uint64_t size, int flags) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->CreateFile(full_path, size, flags);
+}
+
+Result SubDirectoryFileSystem::DeleteFileImpl(FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->DeleteFile(full_path);
+}
+
+Result SubDirectoryFileSystem::CreateDirectoryImpl(FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->CreateDirectory(full_path);
+}
+
+Result SubDirectoryFileSystem::DeleteDirectoryImpl(FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->DeleteDirectory(full_path);
+}
+
+Result SubDirectoryFileSystem::DeleteDirectoryRecursivelyImpl(FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->DeleteDirectoryRecursively(full_path);
+}
+
+Result SubDirectoryFileSystem::RenameFileImpl(FsPath &old_path, FsPath &new_path) {
+    Result rc;
+    FsPath full_old_path, full_new_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_old_path, old_path)))) {
+        return rc;
+    }
+    
+    if (R_FAILED((rc = GetFullPath(full_new_path, new_path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->RenameFile(full_old_path, full_new_path);
+}
+
+Result SubDirectoryFileSystem::RenameDirectoryImpl(FsPath &old_path, FsPath &new_path) {
+    Result rc;
+    FsPath full_old_path, full_new_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_old_path, old_path)))) {
+        return rc;
+    }
+    
+    if (R_FAILED((rc = GetFullPath(full_new_path, new_path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->RenameDirectory(full_old_path, full_new_path);
+}
+
+Result SubDirectoryFileSystem::GetEntryTypeImpl(DirectoryEntryType *out, FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->GetEntryType(out, full_path);
+}
+
+Result SubDirectoryFileSystem::OpenFileImpl(std::unique_ptr<IFile> &out_file, FsPath &path, OpenMode mode) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->OpenFile(out_file, full_path, mode);
+}
+
+Result SubDirectoryFileSystem::OpenDirectoryImpl(std::unique_ptr<IDirectory> &out_dir, FsPath &path, DirectoryOpenMode mode) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->OpenDirectory(out_dir, full_path, mode);
+}
+
+Result SubDirectoryFileSystem::CommitImpl() {
+    return this->base_fs->Commit();
+}
+
+Result SubDirectoryFileSystem::GetFreeSpaceSizeImpl(uint64_t *out, FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->GetFreeSpaceSize(out, full_path);
+}
+
+Result SubDirectoryFileSystem::GetTotalSpaceSizeImpl(uint64_t *out, FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->GetTotalSpaceSize(out, full_path);
+}   
+
+Result SubDirectoryFileSystem::CleanDirectoryRecursivelyImpl(FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->CleanDirectoryRecursively(full_path);
+}
+
+Result SubDirectoryFileSystem::GetFileTimeStampRawImpl(FsTimeStampRaw *out, FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->GetFileTimeStampRaw(out, full_path);
+}
+
+Result SubDirectoryFileSystem::QueryEntryImpl(char *out, uint64_t out_size, const char *in, uint64_t in_size, int query, FsPath &path) {
+    Result rc;
+    FsPath full_path;
+    
+    if (R_FAILED((rc = GetFullPath(full_path, path)))) {
+        return rc;
+    }
+    
+    return this->base_fs->QueryEntry(out, out_size, in, in_size, query, full_path);
+}
diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_subdirectory_filesystem.hpp b/stratosphere/ams_mitm/source/fs_mitm/fs_subdirectory_filesystem.hpp
new file mode 100644
index 000000000..e6c406fa1
--- /dev/null
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_subdirectory_filesystem.hpp
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2018 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+#include <switch.h>
+#include <stratosphere.hpp>
+
+#include "fs_ifilesystem.hpp"
+#include "fs_path_utils.hpp"
+
+class SubDirectoryFileSystem : public IFileSystem {
+    private:
+        std::shared_ptr<IFileSystem> base_fs;
+        char *base_path = nullptr;
+        size_t base_path_len = 0;
+        
+    public:
+        SubDirectoryFileSystem(IFileSystem *fs, const char *bp) : base_fs(fs) {
+            Result rc = this->Initialize(bp);
+            if (R_FAILED(rc)) {
+                fatalSimple(rc);
+            }
+        }
+
+        SubDirectoryFileSystem(std::shared_ptr<IFileSystem> fs, const char *bp) : base_fs(fs) {
+            Result rc = this->Initialize(bp);
+            if (R_FAILED(rc)) {
+                fatalSimple(rc);
+            }
+        }
+
+
+        virtual ~SubDirectoryFileSystem() {
+            if (this->base_path != nullptr) {
+                free(this->base_path);
+            }
+        }
+        
+    private:
+        Result Initialize(const char *bp);
+    protected:
+        Result GetFullPath(char *out, size_t out_size, const char *relative_path);
+        Result GetFullPath(FsPath &full_path, FsPath &relative_path) {
+            return GetFullPath(full_path.str, sizeof(full_path.str), relative_path.str);
+        }
+        
+    public:
+        virtual Result CreateFileImpl(FsPath &path, uint64_t size, int flags) override;
+        virtual Result DeleteFileImpl(FsPath &path) override;
+        virtual Result CreateDirectoryImpl(FsPath &path) override;
+        virtual Result DeleteDirectoryImpl(FsPath &path) override;
+        virtual Result DeleteDirectoryRecursivelyImpl(FsPath &path) override;
+        virtual Result RenameFileImpl(FsPath &old_path, FsPath &new_path) override;
+        virtual Result RenameDirectoryImpl(FsPath &old_path, FsPath &new_path) override;
+        virtual Result GetEntryTypeImpl(DirectoryEntryType *out, FsPath &path) override;
+        virtual Result OpenFileImpl(std::unique_ptr<IFile> &out_file, FsPath &path, OpenMode mode) override;
+        virtual Result OpenDirectoryImpl(std::unique_ptr<IDirectory> &out_dir, FsPath &path, DirectoryOpenMode mode) override;
+        virtual Result CommitImpl() override;
+        virtual Result GetFreeSpaceSizeImpl(uint64_t *out, FsPath &path) override;
+        virtual Result GetTotalSpaceSizeImpl(uint64_t *out, FsPath &path) override;
+        virtual Result CleanDirectoryRecursivelyImpl(FsPath &path) override;
+        virtual Result GetFileTimeStampRawImpl(FsTimeStampRaw *out, FsPath &path) override;
+        virtual Result QueryEntryImpl(char *out, uint64_t out_size, const char *in, uint64_t in_size, int query, FsPath &path) override;
+};
\ No newline at end of file
diff --git a/stratosphere/ams_mitm/source/fs_mitm/fsmitm_service.cpp b/stratosphere/ams_mitm/source/fs_mitm/fsmitm_service.cpp
index 79d490981..0732c0652 100644
--- a/stratosphere/ams_mitm/source/fs_mitm/fsmitm_service.cpp
+++ b/stratosphere/ams_mitm/source/fs_mitm/fsmitm_service.cpp
@@ -28,7 +28,7 @@
 #include "fsmitm_romstorage.hpp"
 #include "fsmitm_layeredrom.hpp"
 
-#include "fs_ifilesystem.hpp"
+#include "fs_subdirectory_filesystem.hpp"
 
 #include "../debug.hpp"