Japan is an... interesting place.
Shinjuku is a good place to stay in Tokyo. I usually stay there when I’m in town. Lots of restaurants, bars, and shopping nearby, and of course, Shinjuku station, which makes it easy to get anywhere once you’ve figured out how to use the JR (protip: if you can’t figure out how much you need to pay for your ticket, but the cheapest one, then use the fare adjustment machines once you get to your destination). It’s also quite close to Kabukicho, which is basically a red light district.
Now, as far as hobbying in Japan, it’s tricky, because it’s sort of legal (paying for sexis illegal, but the legal definition of “sex” specifically means vaginal penetration, so buying a blowjob, for example, is legal), there are places like “pink salons”, which are basically blowjob parlors. As was said above, it’s mostly run by Yakuza and usually foreigners aren’t allowed in these places, but there are exceptions. There was one in Kabukicho that welcomed me (they actually had a barker outside specifically looking for tourists). It was a weird experience. There were only certain girls available to foreigners, and it was a communal room, so you’re sitting in a room getting your dick sucked with a bunch of other dudes getting the same. I had to try it once, but wasn’t for me.
There are also love hotels, which typically have escort services available to service them, specifically. If you get a room there, there will be flyers with escort ads for you to choose from in your room. I do not know if these places service foreigners or not, but you could try.
Worth noting: STIs are quite common at pink salons, including an antibiotic-resistant gonorrhoea strain that started in Japan. They do not use condoms at those places, though you can request that they do. I’d bring your own, though, because the condoms they have there are very small and probably won’t fit you.
In my opinion, Japan probably isn’t worth trying to hobby in as a foreigner. Too few options for us. You’re better off going to bars and trying to hook up with local girls. Quite a lot of them like to fuck foreign guys, it’s sort of considered a cool thing to do amongst young people over there. If you’re somewhat decent looking, aren’t too overweight, and can at least attempt to speak to them, you’ll probably be able to find some action here and there.