Just a heads up: what is being billed as the first "real" karate movie from Japan (as oppossed to Sonny Chiba's karate assassin Street Fighter series) will be hitting theaters in Japan in October. Apparently, plans are in the works to release it worldwide, as well.
The three young men who are the central figures in the story are all up-and-coming karate practitioners, not actors who went through a crash course. They are:
Yagi Akihito - Gojuryu Meibukan
Naka Tatsuya - JKA
Suzuki Yuji - Kyokushin
Joe / TYO