I've never had to change off of Japanese Locale, pretty much every type of symbol seems to work with it for me. The only conflicts I've seen while staying on it is that sometimes, archaic installers will use your locale instead of your system language (resulting in the installer text being in Japanese).
Adding onto this for clarity: the ONLY thing you need to change is your system locale. Everything else can stay in whatever you had it before.
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Make sure you do NOT check the UTF-8 beta. It will cause conflicts with some Japanese games. There is no reason to turn it on, as far as I'm aware.