diff --git a/locales/index.js b/locales/index.js
index 96a1af38b1..9642b400a4 100644
--- a/locales/index.js
+++ b/locales/index.js
@@ -8,6 +8,19 @@ const yaml = require('js-yaml');
 const langs = ['de-DE', 'en-US', 'fr-FR', 'ja-JP', 'ja-KS', 'pl-PL', 'es-ES', 'nl-NL', 'zh-CN', 'ko-KR'];
 
 const loadLocale = lang => yaml.safeLoad(fs.readFileSync(`${__dirname}/${lang}.yml`, 'utf-8'));
-const locales = langs.map(lang => ({ [lang]: loadLocale(lang) }));
+const locales = langs
+	.map(lang => [lang, loadLocale(lang)])
+	.map(([lang, locale], _, locales) => {
+		switch (lang) {
+			case 'ja-JP': return [lang, locale];
+			case 'en-US': return [lang, { ...locales['ja-JP'], ...locale }];
+			default: return [lang, {
+				(lang.startsWith('ja-') ? {} : ...locales['en-US']),
+				...locales['ja-JP'],
+				...locale
+		}];
+		}
+	})
+	.map(([lang, locale]) => ({ [lang]: loadLocale(lang) }));
 
 module.exports = locales.reduce((a, b) => ({ ...a, ...b }));