diff --git a/kanken_online/lang.py b/kanken_online/lang.py
index 209a43d..01f5a72 100644
--- a/kanken_online/lang.py
+++ b/kanken_online/lang.py
@@ -98,6 +98,6 @@ LANGUAGES = {
 
 def localize(text_id: str, language: dict[str, str] = None) -> str:
     if language is None:
-        preference = session.get("language", "en")
+        preference = session.get("language", "ja")
         language = LANGUAGES.get(preference)
     return language[text_id]