It is difficult to get a doctorate in Japan, but even if it is only a minor, it is still a good experience. There must be a broader way to come back.

Japanese professors are generally rigorous in their studies and learn a lot from them.

You study abroad at public expense, and you don't need to work to make money. You should have enough time to study and research.

In addition, it is good to experience different cultures, which will broaden your horizons.

Anyway, it depends on human effort. Good luck!