Grotesque (2009)
Written and directed by Kōji Shiraishi (Noroi: The Curse, Carved: The Slit-Mouthed Woman, Sadako vs Kayako) this is one of the most infamous Japanese exploitation 'gore porn' films (often cited alongside the notorious Guinea Pig series). In the UK it is still banned outright. The BBFC have refused to even certify an '18' version with cuts, stating the film "features minimal narrative or character development and presents the audience with little more than an unrelenting and escalating scenario of humiliation, brutality and sadism".
So, of course it's freely available - completely uncut - on YouTube. Go BBFC.
The plot such as it is centres around a young Japanese couple on their first date. As they leave a coffee shop they're attacked by a man with a hammer. When they awaken they're gagged and shackled in a plastic-sheeting covered basement. For the rest of the film they are abused sexually, and subjected the most horrific, graphic, physical violence and torture . All full-screen and in glorious technicolour.
I can't really say much more about the specific content. If you're okay with extreme exploitation/gore, fine. If you're not, steer clear; there are plenty of reviews/posts around the internet from people who knew the film's reputation and thought they'd be fine with it - only to call it a day before the halfway mark. What I can say is that it's well shot, fantastically lit, and superbly acted by all three leads. The effects are also very convincing. That said, it is - by design - unrelentingly depressing.
I wouldn't buy it - I can't see what I'd gain from another viewing - but I do rate it 7/10