How long does it take to renew a visa in Japan?

Generally, it takes about 1 month. It is better to make other plans when you return to China, or you have prepared all the information for applying for a visa, go to the customs first and set up the country of entry. After returning to China, you can apply again before the visa expires. As long as you apply before the expiration, there is no problem (it doesn't matter if you don't approve it before the expiration). You can control the time yourself, and it is better to apply half a month before the expiration of your visa, which is safer.