I've visited Japan a few times, never looking to hook up but did manage to get lucky with locals twice
First time was about 8-9 years ago. I was backpacking through the Kansai region and was staying at a cheap hostel in Kyoto. I had rented one of their bikes and spent most of the day biking around the city. I was looking for some temple or something like that on the outskirts of the city and stopped at a shinto shrine completely randomly. There was a girl sweeping the steps there so I asked her for directions... I talked to her a bit and turns out her English was OK - she had gone to school at some women's university in Tokyo and had studied English. Instead of telling me where to go though, she asked me to wait a bit. She went to go change and decided to show me the sights herself. Was pretty cool to have a native tour guide showing me around these places most tourists don't usually go to. I spent a few hours with her and I guess we clicked pretty well. Once it started to get dark we headed back to the shrine (her family takes care of the place and she stayed nearby) and she handed me her personal name card - which I've been told is quite common to have over there? Anyway, we ended up meeting the next day in the city at my hostel, went to have dinner, then checked into a love hotel (which actually cost about what my entire stay at the hostel did, but obviously worth it)... I have to be honest, this girl was far from a JAV star - quite plain, didn't wear much makeup, though she had a decently slim and nice body. I guess she was just bored and wanted some excitement, it was certainly an experience for me. I am hardly telling everyone to go camping out at shinto shrines looking for bored jap gals, but sometimes opportunities pop up in unexpected places.
Second time was about 2 years ago and much more typical story - this was a friend of a friend I met at a dinner in Tokyo. I asked her out for drinks on the next day. We hooked up on the third date. She might not "count" - as though she is Japanese she grew up in the US, spoke fluent English and has a western mindset - she even paid for one of the dinners.
So yeah, it's probably a bad idea to try to randomly hook up with the Japanese equivalent of an SPG at a club, but some Japanese are open to other Asians at least... I think being introduced through someone else helps a lot too.