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

https://romeo-wiki.win/index.php/How_to_Bet_on_Horse_Racing_in_Japan_as_a_Foreigner

Gambling in Japan is a curious mix of strict laws and surprising exceptions. While most forms of betting are illegal, a few government-regulated games like pachinko, horse racing, and keirin cycling races offer legal ways to try your luck