I mean, you know, I can't say the Yakuza were directly involved but I can't say they weren't
It's rumored that the Yakuza, also known as gokudō, which is derived from the martial art of judo, which Gene LeBell popularized in America, actually gets it name from an ancient card game, originating from the Nintendo company, which at the time was in the card business, called Oicho-Kabu, which is basically like the Japanese version of baccaract, famous in the media from the British James Bond movie series, which actually began as a book series by Ian Fleming, who served in the Far East in WWII, and whose movies have had multiple wrestlers from Harold Sakata, to Peter Miavia, to Batista in henchman roles, and is essentially the Japanese version of the old Italian Cosa Nostra, also known as the Mafia or Mob, is rumored to have been involved with the death of Rikidozan.