Hi everyone,
I have met and trained on numerous occasions with Su Dong-Chen, as his ex-wife and daughter lived in my city for some time and he came to visit his daughter a fair amount. He spoke very little English at this time (early 2000's), so I understand all this through an interpreter that was with him. He was never Yakuza - he is half Chinese and half Japanese and as so is not very popular with either, and highly unlikely would be admitted by the gang. When he lived in Japan, he was a very well known fighter of great repute. Some member(s?) of the Yakuza didn't like this half-Chinese beating all their fighters, so they sent some guys to 'handle' him. It's been a long time since I heard it, and I was in a group of people so I couldn't always hear exactly what was said, but essentially it started in a bar (Master Su loves his Johnny Walker Red!) and turned into a battle royal in an alley where he was running for his life while fighting these guys with knives. He showed us numerous scars on his arms and such, and said basically "Don't mess with a knife and expect not to be cut/killed". Just the fact that he survived speaks to the realism of his abilities. We hosted seminars, and lots of people from many different styles would come, along with MMA fighters and I never heard ANYone who crossed hands with him say that he doesn't have the goods.
FWIW