Or (and IMHO), what you’re not getting is that they’re just not interested in the Western market. Period.
The few that do bottom, think our dicks are too big, and that’s assuming they can even get past their own xenophobia, which is quiet strong and pervasive. As an American top who likes muscular bottoms, it’s a tough market.
Obviously, I’m painting with a very broad brush, but in general I think you’ll find it true. I’m sure there are exceptions.
If you go through the local agencies, they will do a good job of matching you with whatever it is you seek.
As far as legality is concerned, my understanding is that Japan only makes prostitution a crime when it specifically involves a penis inside a vagina. Everything else is legal. Fair warning, I’m not a lawyer so don’t blame me if you end up in some Japanese jail desperately trying to reach the US consulate. That’s on you.