I have heard by word of mouth from someone who I believe to be in the know that the Yakuza use various Japanese arts, in particular Karate. I do not believe it is mandatory training however and I understand that it is usually secondary to weapon handling.

I've also heard that the Triad used to recruit impressionable youngsters out of MA schools in the countries around where I live as well as in Hong Kong. I do not know whether this is still happening.

Of course this is all word of mouth, I advise keeping away from those people who actually know for sure.
Self Defense
(Website by Marc MacYoung, not me)