Doctors in Japan are monks in the early stage and doctors in the later stage. You can graduate with a friar's degree after completing the doctoral preparatory course. If you want to continue your doctorate, you can only go to the later stage of your doctorate.

After graduating from undergraduate course, China can't go to Japan to take a postdoctoral exam directly. You can only apply for a master's degree from a Japanese university before you can take a postdoctoral exam in Japan or apply for a doctorate. Moreover, you can't take the post-doctoral exam directly, and you must study for a doctorate from scratch. When you start your Ph.D., you can start from the early stage. There is no such thing as a read-only doctor or postdoctoral fellow.