I don’t know why they are divided because they can just change the languages to Japanese or get the Japanese version like other games.

Japanese text speed is very slightly slower, and additionally Japanese runs use a different timing system.

Another question, what about other languages?

Likely just not ran enough to warrant having a board. Plus the boards would begin to look really messy with more languages.

6500 new categories for each spoken language on earth anyone? :-|)