It's a 1970s nunsploitation film from Toie's Pinky Violence. It's got topless whippings, a rape, urination, lesbians and lots of extreme hardline Christian repression. Despite this, though, it's been done in deadly seriousness and it's not camp at all. I wouldn't even call it trashy.
Our heroine is played by Yumi Takigawa, who's still working today. She does lots of things you wouldn't associate with nuns, but that's just letting her hair down before she says goodbye to her femininity and freedom. She calls it "a place where women stop being women."
The convent's pretty extreme. I'm not just talking about the topless blood-stained punishments, but also about the fact that it's a near-totalitarian regime (under the Vice-Abbess) with non-stop doctrinal strictness. Adultery is the worst sin, apparently. Adulterers are no better than animals. They live to be arrested and killed. Any dissenting opinions are shocking and to be punished, e.g. a nun pointing out that we were all born because our parents had sex. The Vice-Abbess's response to that is to go on talking about immaculate conception and the Virgin Mary.
It's genuinely oppressive. It's grim and utterly humourless, although this can paradoxically make the film hilarious when it does something particularly over-the-top or theologically extreme. It's a police state in wimples, with nuns being capable of spying on one another. If someone from the outside comes to see you (e.g. your little sister), it's like a prison visit. You'll be sitting on either side of a grille. There's one other nun here with a rebellious streak and she says she's here because her family wanted rid of her and it was either this or an asylum.
Naturally, the regime's rotten underneath.
Almost all crimes are punished the same way. You'll be stripped and whipped, or some variant thereon. Thus it doesn't make much difference whether you've pilfered food like a schoolgirl, stolen money for your sick father or been caught with your porn stash. (The Vice-Abbess confiscates the latter and is horrified, but then later gets some five-fingered pleasure from it. I don't think she's a hypocrite, though. Instead she's sort of innocent in her thuggish Little Hitler way and this is the first she's known of sinful pleasure.)
This is all a bit trivial for the first half or so, but then it suddenly gets disgusting. Eighteen years ago, a nun got pregnant. What got done to her is bad enough, but what happened to her lover (Fumio Watanabe) is what'll make you want heads on spikes. The woman died. Watanabe kept his post as a revered religious religious leader and is still doing more of the same thing, and worse. (Did I mention that rape?) In fairness, Watanabe's been waiting ever since for God to come and punish him, but his moral anguish doesn't seem to have been powerful enough to keep his dick in his trousers. Naturally, every time he gets a nun pregnant, she'll be pilloried, tortured and called a liar.
As for another nun who "sorted out the problem", she was rewarded for it.
The Christianity is surprisingly well done. Japan doesn't really get that religion and anime portrayals of it can be laughable, for instance, but this film works. They even manage some interesting moments, e.g. Watanabe of all vile people delivering a sermon with genuinely noble and pious sentiments. (He also brings Nagasaki and Auschwitz into the discussion of why God allows suffering, while being super-hairy in a way that you could call either Eastern Orthodox, Jesus squared or the leader of scary religious cultists.) This is more like a medieval convent in certain ways, but that's fine. "I can smell the foul odour of witches."
I also liked the claustrophobic, petty nature of life in this shut-off world. "You gave me valuable information. I'll recommend you for choir membership."
The film's first half is serious and intense about everything, but this just makes it po-faced and not very entertaining. (The exploitation content doesn't affect this at all, oddly.) Then, in the second half, the film's explosive revelations make it horrifying and paradoxically at times hilarious. It's going for everything so hard and seriously that moments of potential camp would instead slay me. That eighteen-year-old flashback of horror becomes blackly funny when the film segues it into traditional Christmas imagery, with a nun carrying a baby into the snowy night. I just about died when this convent turned out to have a trapdoor above an acid bath.
This film's strange. It's sleazy, but also intense and serious to the point of dullness. Then, in the second half, it's staggering and brilliant. Its laughs are explosive because the film's being so sour and straight-faced about it all. It's politically incorrect, e.g. the comedy rape. (Yes, there's also a comedy rape. Takigawa sets it up, it's hilarious and I'm going to hell.) It's utterly 1970s. It's kind of amazing.