[anrakushi]

1. well my experience of seeing basketball played was at university level, so i would disagree. however after university they begin their working careers and of course other priorities come into life other than playing organised sport. This is something that happens all over the world, not just Japan. Once you start your career you tend to spend less time playing sport.

2. I wouldn't say there is a lot, but there is probably not demand for more. There are plenty of Japanese boys who are mad about basketball that they could fill these positions and they are already fluent in Japanese obviously. also Japanese companies would rather hire a Japanese citizen than a foreigner unless that foreigner could offer something special. I just don't know if you can unless you reach high levels of coaching in your own country.

3. slam dunk did create a fair bit of interest in China as well, but anime like this can only keep people interested in something for so long. it was a fad. the people that really enjoyed the sport would have kept playing, the others would have gone on to do something else they enjoyed.

i found another league in Japan that has an east and west conference style set up like the NBA. http://www.bj-league.com/bj/Top.do/|
so i would say with 2 leagues, many people playing in high school and university that Japan has enough interest in basketball. there is not going to be a lot you can offer this country in the sport unless you can achieve some high level of coaching in your own country to prove your worth and learn Japanese fluently. good luck you have many years of work ahead of you.