If you don't go to nightclubs you need to be introduced to a girl by someone else, my wife (who is from Japan) said people will have a house party...like 3 girls...1 girl will invite a guy she is seeing and ask him to bring 2 guy friends. Usually the 1st time you meet your just getting to know them...and exchanging phone numbers/email...then you hook up in the future. Sex is no big deal in Japan...1st couple of dates usually.
It is not like other places where you make eye contact and you hook up...women just walk past you and very rarely check you out. Here in NYC I can just walk past some latin girls and they will start flirting...not like that in Japan.
Now if your american and you run into Japanese girls who are just attracted to american guys...usually white guys...black guys if they enjoy hip hop. Sex is pretty easy.
Not sure about hookers...but Tokyo has a lot of them I hear. Also since fashion is so much in Japan you might mistake a well dressed women for a hooker. I do know that a lot of women will try to blackmail guys for money regarding sex. People worry about being embarresed...so they give the girl money with no questions asked when threatened to going to the cops or telling their wives.
What is popular is the hostess clubs, where a sexy babe will just hang out with you and drink like a companion...and they charge a lot of money. In the last couple of years they have male hostess clubs...where hot MILFs will pay money just to hang with hot guys.
I am no expert but if explored more I am sure you can meet a lot of women into sex...they have a huge adult market over there covering every fetish you can think of.