1, my major.
Needless to say, if the major is wrong, the professor won't want you at all.
2, their English level.
Japanese universities attach importance to English. More important than Japanese. Why? Read technical works and papers in Europe and America. I have a classmate who doesn't have a Japanese proficiency certificate, but he was admitted to an ideal university with more than 770 points in TOEIC English. A classmate took more than 800 TOEIC exams, and just passed the first grade, he was admitted to a first-class university in Japan. A friend was admitted to Kyoto University from the Chinese examination, but he didn't pass Japanese level at all. He went out to study and got the first grade. The professors at Kyoto University College are even more ruthless. It doesn't matter if he doesn't speak Japanese, as long as he knows English. The same thing happened in a famous university in Japan.
3. My Japanese level.
As long as the Japanese ability reaches the normal conversation level, to put it bluntly, what most Japanese universities want is your spoken Japanese ability. Japanese proficiency test 1 is not a necessary condition for entering the university. However, the Japanese proficiency test 1 is the most famous in Japan, and people are often asked whether they have passed the first level during the interview. At the same time, it is also a "hard currency" for international students to find jobs in Japan.
If LZ is confident in the above three questions, you can contact the teachers of Japanese universities through an intermediary, or send an email to the teachers of Japanese universities yourself (unless your resume is tough enough, for example, the TOEIC score is above 850, etc.). Generally, I won't reply to your letter.