Japan is a really weird country for sex. In my experience there (limited, but at least a couple months of elapsed time across multiple visits):
1. prostitution is technically illegal but never enforced. not much different than other asian countries, or england IMO.
2. there are shops that say they do BJ and anal to be strictly legal. but they do vaginal too. the only real plus there is that if you truely want anal, its on the menu in these shops. the girls arent near as pretty as the escorts though.
3. some of these other shops go from the bland to the downright creepy. for instance, there's conversation shops, where you can have a conversation with a girl, drink some tea, etc. sounds nice huh? Now put the girl in a high school uniform, or something even more babylike. then make the girl barely 18. then put a room in the back where guys can go for a few minutes, watch porn of girls in similar outfits getting fucked, jerk off, and then return to the front room and have another cup of tea.
4. there's street vending machines where you can buy used teenage girl panties. out in the open, in the street.
5. theres tons of manga and comic books that deal in teenage girls being kidnapped and raped, on sale in the subway stations.
sorry, but i wouldnt want to emulate japan in this regard.
I stick to escorts when I go to Japan. Its hard enough to get good girls, because the best ones arent allowed to service westerners, because japanese men dont like to touch a girl who has been fouled by a western man.
But better yet i go to other countries, where the people arent so racist and weird about young girls.