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

https://reliabless.com/what-is-the-easiest-legal-bet-to-place-in-japan-with-little-japanese/

Gambling in Japan is a curious mix of strict laws and surprising exceptions. While most betting activities are illegal, locals enjoy legal gambling through pachinko parlours and public sports like horse racing, keirin cycling, and kyoutei boat racing