It’s not a stereotype, it’s a truth. The official name for the fetish is Bura-Sera, which I’m told stems from the term for part of the Japanese schoolgirl’s P.E. uniform.
. . .
Japan has [one of] the largest rape, and other violent pornography industries, and recently placed third world wide in terms of total pornography revenues (2006)
It’s [Safe] been [Safe] suggested that the accessibility of porn, has a correlation to the increase in sex crimes.
Depending on the source, Japan places anywhere from 1st to 54th in the world for sexual assaults. The inconsistency is, of course, due to the number of actual reports, whether or not statistics are based on convicted cases alone, and whether the ranking is per capita.
I think, for Japan, the idea is more deeply rooted in the culture though. I’ve lost track of some of the historical references, but consider Shunga, antiquated wood-block prints of Japanese Erotica. A piece from the late 1800’s entitled
[NSFW] Dream of fisherman’s wife [/NSFW]
depicts the now stereotypical tentacle scenario well before modern pornographic works.
As another example, think about how commonplace a vending machine dispensing the [Safeish] used underwear of [Safe: Snopes] schoolgirls is.
. . .
As for the legal aspect, a lot of the difficulty with convicting offenders of an already notoriously legally difficult crime has to do with the definitions Japan’s legal system has.
Source
The definition of rape in Japan is limited to vaginal penetration by a penis, therefore excluding forced oral and anal penetration and penetration by any other object, as well as rape of men. Forced penetration of these kinds is downgraded to indecent assault. These laws have remained basically unchanged apart from a few minor changes since they were promulgated in 1907
The concept of mens rea in Japanese rape law means that if, from the point of view of the attacker, no harm was meant, no harm was really done. As male and female sexuality are constructed differently, the fact that sexual advances were unwanted from the female point of view does not mean that the male attacker held criminal intentions.
. . .
Kind of tangential:
The idolization and obsession with young girls continues to evolve. Otaku, which traditionally has described anyone with an obsession, has more recently come to describe a different subset of obsession. Some boys, young men, and even men, will fixate on a J-pop idol, and then memorize a choreographed dance so that they can go out to clubs or public performances, perform the dance alongside others, while each attendee becomes mesmerized by an idol on a small stage at one end of the club. This seems to be a release from daytime life expectations, where behavior is serious, composed, and emotions are surpressed. My understanding is that Japanese boys are taught to refrain from expressing excitement or enthusiasm for anything, so the frenetic dance with others has become a [culturally acceptable?] way to channel frustrations with that aspect of life.
. . .
Hope that helps a little bit.