Is that the only thing that's different about Tokyo and Paris? Beijing is over 95% Han Chinese and yet I don't think things look as harmonious.

On another note, I think Japan ends up with kind of a distorted picture since so much of the crime is associated with organized criminal groups with ties to legitimate business and government operating with a degree of openness that I think would surprise most Western observers. Dubro's Yakuza book is a great primer on the topic.