Second, you can contact the school yourself. At present, graduate schools and professors in Japanese universities have their own web pages, which you can check online. You can even contact the professors you are interested in directly, but the exams and various procedures have to pass the university's educational administration courses. I took the exam from Japan, so you must know how to contact the school from abroad.
Three, Japan's top national universities are: Tokyo University, hitotsubashi university, tokyo institute of technology, Osaka University, Hokkaido University and tokyo university of foreign studies. Although you have studied law for half a year, this knowledge is not enough to get you into the law school of a national university. I suggest you consider majors such as literature department, such as Japan International Studies University. If you feel uncertain, I suggest you consider Chiba University, Saitama University and Yokohama National University. It is also a national university.
Fourth, local public universities can also be considered. For example, Shizuoka University in yokohama city university.