I would be interested to know if the reason why (to put it bluntly) porn in Japan is so extreme is due to their cultural repression of sexuality. The reason I ask is that many Asian countries have similar social stigmas around sexuality, and they also have similarly extreme forms of porn.
Not to mention the existence of hentai, yuri, and ecchi. All of which don't really have widespread western equivalents, despite western cartoons being fairly popular.
Hentai etc are descendants of shunga pics; you've probably seen Hokusai's "The Great Wave Off Kanagawa". You may have seen "The Dream of
The Fishermans Wife" (NSFW)
In social interactions maybe ? Japan seemed to be a very repressive/elitist society. You had to be polite in everything, and sexuality is often the opposite of that (you could probably have sex through polite chat beforehand, but I'm sure it requires maturity that most people don't have)
Just because people have a different view of sexuality, and confine it to a specific time and place, doesn't mean that it's a repressive society. You have to realize that most Asian cultures are heavily focused on context, and place, and not just the pure, isolated act.
I remember reading an article talking about how all the tentacle porn in Japanese hentai exists because USA banned the depiction of genitalia in the media after WWII, so they had to become creative about it.
Actually it's the other way around.
Post WW2 the allies actually removed most of the censorship laws.
But the premise might be correct tho the material predates Allied occupation by 150 years.
Not to mention the existence of hentai, yuri, and ecchi. All of which don't really have widespread western equivalents, despite western cartoons being fairly popular.