diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..19faf26
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "simple-protobuf"]
+	path = simple-protobuf
+	url = https://github.com/fumiama/simple-protobuf.git
diff --git a/simple-protobuf b/simple-protobuf
new file mode 160000
index 0000000..e0b88c0
--- /dev/null
+++ b/simple-protobuf
@@ -0,0 +1 @@
+Subproject commit e0b88c0c63a9f2afb05693b3bae92d94bdd12d51