In fact, I studied Japanese in Changchun, and many people came back from studying in Japan. Besides, it is not so simple to start a school now, especially now. Even if it is done, enrollment is still a problem. Besides, you can't teach yourself. You have to recruit teachers. Besides, you can't start school just because you come back from studying in Japan ... you need a teacher qualification certificate. ...
There are many cram schools and the like. But you have to operate slowly to go public.