diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..ca47f53
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "mkdocs-ivory"]
+	path = mkdocs-ivory
+	url = https://github.com/daizutabi/mkdocs-ivory.git
diff --git a/mkdocs-ivory b/mkdocs-ivory
new file mode 160000
index 0000000..8d8a9ac
--- /dev/null
+++ b/mkdocs-ivory
@@ -0,0 +1 @@
+Subproject commit 8d8a9aca05f611ea1f2742341219bd61b5852c9d