I think you would have a very good chance at getting on as CFI with the school you choose to train at. You will finish out the visa term with 1500hrs, hopefully some multi engine time in there also. The question is what to do next?
U.S. route: U.S. regional or cargo-not likely due to visa restrictions=return to Japan.
Canada route: Train then regional or cargo=experience=go overseas and make $$. From the above post this sounds likely after being granted permanent status, with your education and training this should be no question but I’m not Canadian so..
Return to Japan route: convert to ppl and test for cpl, more money, will you be employable with 1500hrs in Japan?
What about China with FAA CPL multi & 1500hrs?
The wild card-go to U.S. for training, are you handsome and charming? (JK)
https://flyhaa.com/admissions/intern...dents/f1-visa/