diff --git a/README.md b/README.md
index e5d428a..aa03040 100644
--- a/README.md
+++ b/README.md
@@ -89,7 +89,8 @@ PandAへの負荷を軽減するために課題・クイズ取得にキャッシ
 - 2021/05/16 v3.4.3 小さなバグを修正。
 - 2021/05/17 v3.5.0 カラーユニバーサルデザインに対応
 - 2021/05/17 v3.5.2 締切が14日以上の課題も色付けするように
-- 2021/11/24 v4.0.0 [Comfortable-Sakai](https://github.com/kyoto-u/comfortable-sakai) を移植。
+- 2021/12/22 v4.0.0 [Comfortable-Sakai](https://github.com/kyoto-u/comfortable-sakai) を移植。
+英語対応、その他内部処理の改善
 
 
 # コンパイル方法
diff --git a/README_en.md b/README_en.md
index dfbdf7b..82f872e 100644
--- a/README_en.md
+++ b/README_en.md
@@ -93,6 +93,7 @@ The cache time can be changed in the configuration.
 - 2021/05/17 v3.5.0 Support for color universal design.
 - 2021/05/17 v3.5.2 Color code assignments with due date more than 14days
 - 2021/11/24 v4.0.0 Merged [Comfortable-Sakai](https://github.com/kyoto-u/comfortable-sakai).
+Now supports English locale. Re-wrote codes.
 
 # How to compile from source code
 - Run
diff --git a/manifest.json b/manifest.json
index d0e5832..13a8290 100644
--- a/manifest.json
+++ b/manifest.json
@@ -3,7 +3,7 @@
   "description": "__MSG_EXTENSION_DESCRIPTION__",
   "version": "4.0.0",
   "manifest_version": 2,
-  "default_locale": "en",
+  "default_locale": "ja",
   "icons": {
     "16": "img/icon16.png",
     "48": "img/icon48.png",