Where you find casual sex online in Tokyo (Japanese girl)

Do you know the Japanese phrase called " nanpa" ?

" nanpa" means picking up random strangers. You can do nanpa on the street, bar,night club etc.
You can also use some dating site to do nanpa.

Nanpa (ナンパ), also transliterated as nampa, in Japanese culture is a type of flirting and seduction popular among teenagers and people in their twenties and thirties. When Japanese women pursue men in a fashion similar to nanpa, it is called gyakunan (ギャクナン)

I think JapanCupid.com and Asian Sex friend finder are good for English user. and there are more chance if you use local dating sites like Love search,Wakuwaku mail ,and Happy mail etc.

first date to first sex is higher in Tokyo than almost anywhere else.

There’s so much available sexual massage shop in Japan. Some are okay to enter for foreigners.
See Pink salons in Tokyo Japan

You can also check Bulletin boards like Craigslist, metoroplice, TNB etc.
There is a casual encounters section in Craigslist.