As someone currently living in Japan and worried about my social circle (though working, not studying), I feel like I should have more helpful things to say than I do.
Regarding the main question, I would say that if you ever decide in the future that an IRL circle of friends is valuable, anecdotally it's much easier to make friends in college than after. Like an infomercial would say, you should act now. Of course, not all friends will be preserved in the transition after graduation so it might not be worth the move.
In a more general vein, what are your plans for the future? You list many important considerations for your present situation, but without much focus on how they'll affect you later.
Finally, I do think it should be absolutely possible to make friends in Japan, especially since either your university is English-friendly enough that there are other foreigners around, or your Japanese is good enough despite being non-native to communicate effectively.
Ooh, that's hard.
As someone currently living in Japan and worried about my social circle (though working, not studying), I feel like I should have more helpful things to say than I do.
Regarding the main question, I would say that if you ever decide in the future that an IRL circle of friends is valuable, anecdotally it's much easier to make friends in college than after. Like an infomercial would say, you should act now. Of course, not all friends will be preserved in the transition after graduation so it might not be worth the move.
In a more general vein, what are your plans for the future? You list many important considerations for your present situation, but without much focus on how they'll affect you later.
Finally, I do think it should be absolutely possible to make friends in Japan, especially since either your university is English-friendly enough that there are other foreigners around, or your Japanese is good enough despite being non-native to communicate effectively.