Beautiful country. I had a Japanese "green card". Strip clubs, massage parlors, blow-job cafes/bars, and some escorts are accessible to foreigners. Some knowledge of the language AND persistence pays off. I had my favorite titty bar, the girls loved me, but it was work to find it, and took some work to establish trust.
Geishas and the high end stuff would be off limits. The red light district in Tokyo was crawling with Nigerian pimps. Those fuckers were a pain in the ass and I don't know why the Yakuza tolerated them. Kobe, Kyoto and Osaka had a Japanese controlled sex trade.
nigerians?what the hell are they doing in japan?and as for the yakuza putting up with them,they probably kick a decent amount of money up to them.