Oshima who died several weeks ago should be mentioned along with Akira Kurasawa whenever you are talking about Japanese cinema. Specifically, Japanese New Wave (ヌーベルバーグ from the french nouvelle vague) or the difficult to define Pink Film genre.
In Realm of Senses, as discussed by Dana Stevens at Slate, was intentionally made to push the boundaries of Japanese censorship at the time, and several sections of the film had to be physically developed in France to avoid prosecution. Just a warning that this clip is NSFW.
But one of my first recollections of Japanese cinema was of David Bowie and Takeshi Kitano in Merry Christmas, Mr Lawrence. I was possibly very young when I first glimpsed as it seems to have entered my conscience at a young age. Although it wasn't until much later that I sat down and watch it.