Shin-sama
The basic principles of Buddhist practice are listening, thinking, and practicing.
Listening means listening to the teacher's teachings. Of course, even if it's not directly, you can also learn from papers etc. where the pioneers explain it.
Thinking is to repeatedly think and deeply understand what you have been taught.
In training, you will actually practice the content you have deeply understood and make it your own.
If you want to learn Buddhism in a general and systematic way, how about being a member of society gradually taking courses at Nakamura Former Oriental Institute and Oriental Gakuin from the field you are interested in?
http://www.toho.or.jp/
Alternatively, there is a place called Tokyo International Buddhist School by communication.
http://www.tibs.jp/
Please consider it.
Kawaguchi Hidetoshi Gassho