AI PhD graduate seeking job in Japan

Hello everyone. I am seeking suggestions about seeking a job and move to Japan. I know Japan is a very attractive country appealing a lot of foreigners to move to work and live a life. I am one of these foreigners but has some different personal situations. Appreciate your patience if you would like know me more.

1. My major is IT/CS/AI/Finance. I obtained my master degree of CS from China and now studying an AI PhD in Australia (not top University, but 1 paper accepted by ICML). Something different is that I obtained my bachelor degree of Finance from China, a major quite different from CS.

2. I want to seek a job in companies but have little formal working experience. As a PhD student, I wonder whether can I find a job in Japanese companies at my case without working experience, 30-year-old female? I heard that Japanese companies prefer young candidate if they don't have working experience. How can I handle this weaknesses? Will PhD overqualified?

3. Is post-doc programs a good stepping stone? I think finding a post-doc program may be easier than seeking a job in a company, but I wonder if I finally want to work in a company, will a post-doc program be a detour and make it more difficult to find a job in companies.

4. International relationship is unstable. I heard the relationship between Japan and China is currently tense. Will this affect Japanese companies make a decision to hire a Chinese employee? Or will it become more difficult to apply a working visa?

5. Language capability. I passed N1 test 10 years ago, but has little chance to practice writing and speaking. Will improving Japanese skills really help a lot in finding a job? Will the interview usually be conducted using Japanese?

Appreciate your reading and welcome any discussion.