Do I have to take off my shoes when I enter a Japanese restaurant in China?

Obviously not. From my professional point of view, the following points are enough for customers to eat without taking off their shoes:

Do as Romans do in Rome. Since it is a Japanese restaurant in China, there is no need to care too much about Japanese etiquette.

In China, a populous country, the business in the store will not be too bad. How smoky it would be if everyone took off their shoes and went in.

Judging from the quality of China people at present, there is no guarantee that customers will not spit or anything else in the store. If they take off their shoes and get dirty, your feet will be embarrassed.