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

https://varimail.com/articles/what-is-the-best-first-legal-bet-in-japan-for-a-newbie/

Gambling in Japan is a curious mix of strict laws and surprising exceptions. While most forms of betting are illegal, you’ll find legal thrills in pachinko parlours and popular sports like horse racing, keirin (bicycle racing), and kyoutei (boat racing)