It's the first in what became an exploitation series, about women in prison. It's arty sleaze that you can argue contains political subversion, genre deconstruction and/or a female empowerment message. It's ultimately a revenge movie, in which the heroine (Matsu the Scorpion) makes certain people regret doing unforgivable things to her.
However it's also so nasty and sleazy that it's a bit boring. I'd been planning to watch the whole series, but I've abandoned that idea. The film's problem, for me, is that it's insufficiently Matsu-centric. She's in it, but she rarely speaks. Her story role tends to be reactive, although admittedly you might expect that given the setting. There are times when we leave the prison (e.g. the flashback from three years earlier, while she was still a free woman), but a lot of the time she's just another of the prisoners. Brood silently, get naked, get tortured, inflict violence. Repeat.
She gets a fair amount of screen time, but I never really felt as if I was primarily watching the story of a protagonist. You might have to pay attention to remember which one she is. In practice, the evil scumbags stand out far more. Their scenes I'd be interested in, but the mistreatment of the inmates in general tends to get dull. Look, the guards are being scum. What a surprise, they're revolting in this later scene too. And again. And again. Now the girls are having to dig lots of holes. How, um, interesting. You'd expect female torment to be at least shocking, but those scenes don't really go anywhere and you don't expect them to.
That said, though, the film isn't being subtle about its politics. (I laughed at the scene where the prison governor is shouting at everyone as if he doesn't have a foot-long shard of glass in his eye.) The Japanese flag is shown more than once, each time subversively. The prison governor congratulates his guards on their service for their country just as a prisoner is escaping. (His commendation document gets blown away and stamped on in the rush.) A banner to celebrate the "beautiful soul and harmony of Japan" is seen hanging alongside the lynched corpse of a yakuza boss who got Matsu raped, beaten and ultimately sent to prison, with the help of a corrupt cop.
The prison is outrageously nasty. It's so cruel that it becomes both absurd and predictable. However a line is clearly being drawn with Japan itself, with power going to the most stupid and ruthless (always men) while everyone else (i.e. women) gets crushed underfoot. It offers plenty of examples of the powerless siding with their oppressors and competing to outdo them for sadism, though. These evil bastards deserve everything that's coming to them. We meet:
(a) loathsome, leering prison wardens who'll unjustly punish or even strangle to death the people they're looking after.
(b) trusties who are arguably even worse. Normal inmates wear blue, while trusted inmates wear orange and are allowed to torture the other girls. I don't think they're trying to gain anything from doing so. It's just sadism.
(c) the men in power in the real world outside. The worst deeds in the film are committed by these people.
There's surrealism. Matsu's flashback sequence is presented like a stage play, with a revolving wall to change the set for the next scene. There's a shower room knife fight where nightmare lighting and kabuki-like blood patterns make one of the girls look like a demon.
There's lots of nudity, of course. It's a 1970s "women in prison" exploitation film. What did you expect? However there's only one scene of lesbian sex and all the nudity is in a grotesque, unpleasant context where any attempt by the audience to leer is being thrown back at us by warders doing exactly the same. If you find this sexy, get the hell away from me. Men are leering over, torturing and humiliating women. There's a line of male warders watching in the women's communal showers, for instance.
(Ironically, Meiko Kaji played Matsu after changing studios because her last one, Nikkatsu, had switched over to making Roman Porno adult films. This was her first nude role.)
It's based on a manga, incidentally. Personally, I'd call this film trash, but made by an arty director who's trying to be subversive. It's quite an interesting film to talk about, both stylistically and in its subtext. Gender and power relations, politics, etc. It portrays a literal revolution! At the end of the day, though, it's also so trashy that I only cared intermittently about what was on screen. I said there was only one lesbian sex scene, but it's between Matsu and her cellmate while they're in solitary confinement together. That's an odd definition of "solitary". (Unless maybe it's a subtitle mistranslation?)
The film series is known as Female Prisoner Scorpion. I'll be avoiding it. There are a couple of similar films that interest me, e.g. the one starring Asami, despite its disturbing title. For the most part, though... no.