I live and work in Japan, and wish you the best of luck, your going to need it.
The Japanese Sex Industry is HUGE, but it is also racist in its treatment of non-Japanese customers. Unless you know at the very least basic Japanese, enough to deal with the touts, you are not going to get into a lot of shops.
Their is a great deal of anxiety about the language difference, and even if you do speak Japanese well, most of the high end shops will not serve you.
Their are escort services that specialize in Gaijin (foreign) clients, but expect to pay US rates or higher ($300 to $500 an hour) with an average girl.
You have to have connections to get into the better shops, where you will meet the AV girls you seek. If you are here on business, drop a few hints to your Japanese counter-part that you are interested in going to a "fashion health" or "soapland". It is pretty common for salarymen to visit these places, and it does not have the same stigma as in the States.
If you do have language skills, you can visit the previously mentioned districts in Tokyo, or if you are coming to the Osaka area, hit Umeda and Namba.
Also, your best luck in grabbing a Japanese girl is actually just hitting a Gaijin Bar. The "Sam and Dave's", "Bar Isn't It" and "Pig and whistle" chains are famous for easy pick-ups. They have locations in most larger cities, and since a lot of the Japanese girls there are looking for a western boyfriend, a freebie is pretty much a sure thing.
Understand that paying for vaginal intercourse is against the law, but paying for anal sex isn't. I know, it makes no sense, but this is Japan. They pixelize porn between humans, but it is legal to show a woman fuck a dog. Once you except the logic of this, it all becomes easier to live here.
The reason I mention this is that most shops are little more than blowjob bars. If you want sex, you need to pay extra for the "AF" option (anal fuck). It will be on the menu at the front, but it may be in Japanese, so if you see a selection of services and one is ¥10,000, just pick that one, it is the one you want most likely.
Now, I have never actually had a girl insist I fuck her in the ass after paying for the AF option, most will let you fuck them any way you like, but remember to not force the issue.
And this is my last point. You are not breaking any laws. As long as you are not paying for "vaginal intercourse", you are perfectly legal. BUT, these shops are mostly owned by the Yakuza (Japanese Mafia), so if they refuse to let you enter, or ask you to leave, I suggest you do it in a polite and fast manner.
I have lived in Japan for 10 years, and have only heard of one incident when the Yakuza attacked a Gaijin, but it was a co-worker of mine that kicked the guys ass in a club. He won that round, but when he exited the club, the guy ran over him FIVE times in his Range Rover. DO NOT MAKE THESE GUYS LOSE FACE, they will kill you.
Be polite, speak as much Japanese as possible, and good luck!
