It's actually a lot more depressing than anything that's been said here. The fact is, young Japanese people just don't have the time or energy to put into a sexual, or even a romantic relationship, and it's primarily because of the Japanese work culture. Most Japanese men work up to 10-14 hours a day, 6 days a week, and go out to eat and drink with their colleagues after work up to midnight because, well, that's what Japanese culture says working men should do. So they simply don't have time to commit to a relationship.
According to a government survey, more than a quarter of unmarried men and women between the ages of 30 and 34 are virgins; 50 percent of men and women in Japan said they were not “going out with anybody.”
http://www.nytimes.com/2009/07/26/magaz ... wanted=allNow, we can make fun of the content of that article, lonely guys falling in love with anime characters or dating sims, but that is a serious quirk with some justification. Why bother with a real relationship with a woman who might end up unhappy with you, thus making you more unhappy because you are unable to please her, when you can have a perfect, idealized simulation that is always happy to see you, can be seen whenever around your insane work schedule, and "loves" you unconditionally? When it gets put like that, it makes all those H-game dating sims a bit less creepy... well, most of them, anyway.
So, yeah, Japanese men are under too much pressure to perform in the workplace to devote time to families. Add in factors like the changing job market, the fact that part-time jobs are frowned upon, the overall lack of psychological counseling, and the perceived high standards of Japanese women, and it makes sense that more and more Japanese men are
withdrawing from society altogether. "You bring shame and dishonor to your family!" is a bit of an Asian stereotype, but it does have roots in reality. There are a lot of problems in Japan, and it does stem from a lot of the culture.