Posting this here as it might help with weird bugs that occur long after the cause:
I get it, you switch locale to Japanese to run some crazy game and it worked! However, down the line, other things stop working. The locale change makes Japanese stuff work, but it can make other stuff fail, particularly things that rely on the various accented characters of European languages or UTF-8 encoding.
Empirically, what seems to happen is that when some programs are installed or updated, they pick up the new localisation, and set themselves up accordingly. This is certainly the case for Java, which likes to update and can be quite naggy about it.
Once the localization is baked in this way, changing your locale back to your native one doesn’t fix the problem! You either have to wait for the next update, or actively uninstall and re-install the affected program(s).
So, in short, don’t allow updates to run while your locale is set to a non-native one! Or if you did, switch back to your native locale and re-install whatever updated.