Tokyo's redlight district is in an area called Roppongi, seems like theres something there for everyone. If you can't find service from japanese girls, i think theres a few clubs there with caucasion women. Specifically, there was a club i checked out called Club Lex that i was referred to by a japanese guy that had specifically caucasion women, or many caucasion women were hanging out there anyways.
Its true about westerners having an easier time picking up japanese chicks though, the society itself is so respectful, and honour is so important that when they see liberal minded westerners dancing and having a good time in the clubs and whatnot the women seem to let there gaurds down a bit to have a good time. It makes it a much easier introduction and in those kinds of environments where women are of looking for some male interaction it naturally leads to an easy hook up. Good luck!