diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 000000000..78bce0ee5
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "core"]
+	path = core
+	url = https://github.com/pqrs-org/KE-complex_modifications-core.git
diff --git a/Makefile b/Makefile
index d20b4a376..b4a630917 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ all:
 	@echo "============================================================"
 	@echo
 
-	bash scripts/update-json.sh
+	sandbox-exec -f core/files/generator.sb bash scripts/update-json.sh
 	python3 scripts/lint-src-json.py src/json
 	python3 scripts/lint-public-json.py public/json
 	ruby scripts/lint-groups.rb
diff --git a/README.md b/README.md
index c854e294b..701d485b8 100644
--- a/README.md
+++ b/README.md
@@ -9,9 +9,17 @@ complex_modifications for Karabiner-Elements.
 
 ## Add rules
 
-1.  Put a JSON generator file (`.rb`, `.erb` or `.js`) into [src/json](https://github.com/pqrs-org/KE-complex_modifications/tree/main/src/json).
+1.  Clone repository.
+
+    ```shell
+    git clone --depth 1 https://github.com/pqrs-org/KE-complex_modifications.git
+    cd KE-complex_modifications
+    git submodule update --init --recursive --depth 1
+    ```
+
+2.  Put a JSON generator file (`.rb`, `.erb` or `.js`) into [src/json](https://github.com/pqrs-org/KE-complex_modifications/tree/main/src/json).
     (Or put a `.json` file directly into [public/json](https://github.com/pqrs-org/KE-complex_modifications/tree/main/public/json) directly.)
-2.  <details>
+3.  <details>
     <summary>(Optional) Update <a href="https://github.com/pqrs-org/KE-complex_modifications/tree/main/public/groups.json">public/groups.json</a> if you want to add your rules into specific category.</summary>
 
     Add the following entry into `groups.json`.
@@ -25,7 +33,7 @@ complex_modifications for Karabiner-Elements.
 
     </details>
 
-3.  Run `make` command on Terminal. <br/> If you've a generator file into `src/json`, formatted json file will be auto generated in the `public/json/your_awesome_configuration.json`.
+4.  Run `make` command on Terminal. <br/> If you've a generator file into `src/json`, formatted json file will be auto generated in the `public/json/your_awesome_configuration.json`.
 
     ```shell
     make
diff --git a/core b/core
new file mode 160000
index 000000000..6165ec387
--- /dev/null
+++ b/core
@@ -0,0 +1 @@
+Subproject commit 6165ec387ae53e4590fbf51fdf0f468cc88bdb49