My gym (in Tokyo) is full - I mean FULL - of Yakuza and there are a lot of tattoos, but they keep them covered up.
I know one guy, an enforcer-fighter type who has a full Irezumi "suit", and the pearls in the dick deal. Well mannered guys, but I don't care how much bigger I am than him, I would not mess with him...
My gym's parent company reportedly has Yakuza connections, and hence the lack of prohibition common in so many other gyms. Then again Yakuza connections in business are pretty common.