I would guess that what most refer to "Japanese Billiards" is in fact a billiard game played with 4 balls. Most of the older players that I know here in Japan often tell me that they've been playing for more than 20 years, but "back then, it was all "yotsu tama." Yotsu=4 Tama=ball Don't know much about it, but it's a game called 4-ball if you translate it directly. Have never seen it played, but all the old timers played it exclusively back in the day.
Today in Japan, all players and bangers alike play primarily 9-ball. Once in a while, you'll see a couple of house pros messing around with 14:1, but not playing seriously. The pro tour has an 8 ball tournament every once in a while, but many of the pros pass. One pocket doesn't exist.
However, there is a nationwide amateur organization that is divided up into prefectures (or by state) that is exclusively rotation. It's all based on a point system, with the top teams and individuals competing for state and national titles. There's no money in it period, so often times, the best in the state is NOT really the best player in the state.
dave