I might as well toss in a reply.
I live in Fukuoka city, which is in Kyushu, and I walk alongside the city's giant red light district almost every day on my way to work. I've never gone inside any shops, but I have male friends who have, and also female friends who work or used to work in there.
To me, it's all really sad. You might look at the variety and the scale of the sex industry and think that the Japanese are a bunch of liberated, fun-loving party animals while people in the west are Christian prudes, but that's just not right. Of course this is all relative, but people here in Japan are lonely, oppressed and miserable. Communication and expectations between the two genders are terrible. Fewer people are in satisfying relationships, fewer people are having sex that they don't pay for, and even when they do pay, it doesn't help the fact that Japanese people have relatively little human contact.
It's a deep-rooted part of the culture that people keep high physical and emotional barriers around themselves, but this creates problems, and the sex industry is basically the symptom. People buy and sell affection because they're starved of it. Women buy it, too, although they pay less for sex and more for simple conversation. Where else in the world do people regularly spend hundreds of dollars just to have someone be really nice to them for an evening? Other East-Asian countries, I suppose. Call me a narrow-minded westerner, but I think that is really f*cked up.
I'm sorry to get so negative on the Japanese. It's a beautiful country, with kind and intelligent people, as well as a clean and safe living environment. The lack of crime is amazing. It's not easy to find happiness, though. In June, I went back to America for the first time in a few years, and I had forgotten, partially, how different it is back home. I was so startled by the shift away from these problems when I got off the plane that it's made me think more about moving back than anything else has since I arrived.