Requirements for earning a Master's degree in Computer Science in Japan

Hello,
I took 80% of the required Computer Science courses in my undergrad degree in America but I also changed majors to Japanese before I graduated, so I did not graduate with a major in Computer Science.

I studied abroad in Japan for 1 year and also worked in Japan as an English teacher for 2 years (so I’ve already lived in Japan for 3 years total). My Japanese fluency is almost N1, which I plan to take this December, and again in July if I don’t pass on the first time.

I want to pursue a Master’s in Computer Science in Japan to have a qualification and also because I personally just want to study again and refresh my Computer Science knowledge, but since I don’t have the matching undergraduate major…is it still possible to enroll in a program in Japan? I’d rather not go back to undergrad…
I’m also not really in touch with any of my old Computer Science professors in college to write me a letter of rec, only my English teaching co-teachers and supervisor (in Japan from 1 year ago and now currently in Korea).

Is it still possible? Thank you!

This is something I’d suggest researching yourself. A preliminary search shows that University of Tokyo has public information about the grad school application process. It looks like you need to find a professor willing to take you on and pass a test.