This is quite scary actually in what it reveals about the Japanese national psyche. You should be warned that this is far from tasteful, and probably quite disturbing…
The law still exists today that you can’t show genitalia or pubic hair in Japan on TV, in magazines or on video. Some years ago, animators and artists were looking to find new ways of delivering ever more explicit material to sex-starved salarymen and over active boys.
The solution was simple, and as usual with many things Japanese, inexplicable. You couldn’t show a woman having sex with a man, so instead why not an animal? And what better animal than an octopus? After all, it has 8 phallic appendages ready and waiting for some hot schoolgirl action. And unfortunately most of the time it is schoolgirls, and unfortunately most of the time it is unconsentual.
Apparently the thought of marine animal bestiality rape was nowhere near as harmful as the idea of sex between two consenting humans. Thus it was allowed, neatly circumventing the censorship, substituting it for something undeniably more lurid and distressing and giving birth to a whole new genre of pornography, which is now incredibly popular. So popular in fact, that many video stores have an entire section devoted to it.
The most famous film is Legend of the Overfiend which has been described as:
“.. the the most famous tentacle rape and super-violent horror in the history of anime.”
I would be worried for any person that actually found entertaining a film described in this way.