Looking for someone in Japan

Theoretically, it can be found, although it will be very troublesome. If you use official means, through the police station and the local government, you should be able to find it.

However, it is hard to say whether the Japanese official institutions will accept your application. After all, I don't know why you are looking for him. If there is a very important justifiable reason, you can contact the Japanese embassy or consulate in China, and then find the local police and government after the proof.