Gambling in Japan is a curious blend of strict rules and surprising exceptions....

https://wiki-global.win/index.php/Are_There_Classes_to_Learn_Horse_Racing_Betting_in_Japan%3F

Gambling in Japan is a curious blend of strict rules and surprising exceptions. While most forms are illegal, you can still try your luck at pachinko parlours, horse racing, keirin cycling, and kyoutei boat racing