Here is the photo of the top 95 Yakuza bosses of Yamaguchi-gumi (which controls 70% of all Yakuzas in Japan)
http://blog-imgs-43-origin.fc2.com/r...ouryokudan.jpg
You can see half of them look just like salary men out there on the street and they actually are. A lot of them are more like crooked, unscrupulous business men who don't have any conscience. So I'm sure they would love to have foreigners who were like ex-Goldman and Sacks traders who got kicked out for their shady business, but in reality, the prerequisite for being Yakuza is to go to prison and foreigners will get deported if they are convicted of a serious crime, so practically Yakuza jobs are limited to Japanese and Koreans with a special permanent residency.