Gambling in Japan is a curious mix of strict laws and surprising exceptions....

https://wiki-nest.win/index.php/What_is_a_Keirin_Velodrome_and_Can_Tourists_Go%3F

Gambling in Japan is a curious mix of strict laws and surprising exceptions. While most betting is illegal, you’ll find legal outlets like pachinko parlours, horse racing, keirin cycling, and kyoutei boat racing