According to personal experience, there are three forms of going to Japan for graduate study.

Go to a language school

While studying in a language school, I am going to take the postgraduate exam in Japan.

Learn from a graduate tutor.

It is purely compulsory to go to a Japanese school to study some topics with the tutor of graduate students. After getting familiar with the tutor, you will be more likely to take the postgraduate exam in this school.

Participate in the international education exhibition

Through the annual China International Education Exhibition, there are such large-scale exhibitions in Beijing, Shanghai, Guangzhou and other places in March and June, and some schools, embassies and consulates, joint schools and intermediaries from the United States, Britain, Canada, Australia, New Zealand, Europe and Asia will participate in this exhibition. There are also Japanese schools, you can try it at the exhibition.