How long can I stay in China after getting a Japanese visa?

First of all, the types of visas you get are: emigrating to Japan, traveling to Japan, studying in Japan, etc.

But it's all the same reply. There is a departure date on the visa. If you are traveling, you can leave Japan within the validity period. When to go to Japan (that is, how long do you want to stay in China) is none of your business. It depends on how many days you are going to Japan. Grasp the expiration date and just leave Japan.

If you immigrate to Japan, the same problem will be reported at the latest.

Have a nice trip!