The book I'm writing is set in Japan and there's a scene where the yakuza is mentioned but I'm not sure if I should call it "yakuza" or "underground world" or what. I don't think I hear "yakuza" that often when I watch Japanese dramas or movies, so I don't know if it's kind of like Voldemort's name, too scary to say it out loud, or it's just my imagination. What would a Japanese person say? Specifically, it's someone saying they suspect somebody else is linked to the yakuza (not saying it to that person).
Yakuza is like the mafia, But in Japan, they are very organized, do business politely and most Yakuza members actually pay their taxes to stay on the right side of the law. bÅryokudan is the word used by the media to describe Yakuza. It broadly means violent group.