Add and fix Japanese localization

[noritada]

This PR adds translations for some messages, and also fixes some existing translations.

Dear @Hima-Zinn @tkusano @dolciss @oboenikui I would appreciate your review and feedback on these text updates.

Many thanks!

[ansh]

Thank you! And thank you for tagging the other contributors. Looking forward to getting some consensus from the other native Japanese speakers.

[noritada]

@dolciss Thank you for your review! I have applied your suggestions to remove notation inconsistencies, etc.

[dolciss]

@noritada Thanks for applying! LGTM