I believe it's the first live-action film based on Maicchingu Machiko-sensei, the children's manga and anime about a teacher whose clothes keep falling off. It's terrible, but not entirely without charm.
The interesting thing about it is its director, Minoru Kawasaki. I like him. I think he's wonderful, even if the actual films he makes often don't quite work for me. He's an absurdist with a surprisingly wide range, with work including:
1. Parody sequels/remakes of relatively well-known serious movies (e.g. Japan Sinks, The X from Outer Space)
2. Domestic-scale human melodramas that are being played completely straight except for the protagonist being a comedy rubber monster (Executive Koala, Crab Goalkeeper)
3. Low-budget straight-to-video comedy nonsense with nudity (Maboroshi panty vs. Henchin pokoider, Ah! There Is No Toilet In This House).
This is the latter. Firstly, there's the source material. Machiko-sensei is a teacher who manages to end up disrobed in public at least once an episode. This is a children's anime that ran for 95 episodes. They wouldn't be able to make it today.
There are two obvious problems with turning this into a live-action film, even a knowingly silly one like Kawasaki's. The first is that Machiko doesn't really seem too bothered by her clothes falling off. She won't always even notice. She'll get embarrassed and say "maicchingu", but that's all. Now you can do that in a cartoon, but in live-action it's hard to convince the audience that, for instance, Machiko hasn't realised that her sweater caught on a nail as she was running along and has now completely unravelled, leaving her topless. You'd notice. Not noticing would make you look mentally impaired.
The other problem is the cast full of perverts. Machiko's students grope her, look at girls' panties and don't even think they're doing anything wrong. The teachers are just as lecherous, albeit fortunately better behaved. This was bad enough in the anime, but in live-action it could easily get repellent or disturbing.
As it happens, Kawasaki overcomes the first problem with bad acting and the second problem (partly) with amiable ludicrousness.
This is a very silly and badly acted film. The former is deliberate and the latter is almost part of its charm. The plot is a thin tissue of random episodes, mysteriously interspersed with music videos in which Machiko-sensei does her famous "maicchingu" pose in, say, heavy metal or Hawaiian styles. The backgrounds of these are liable to contain silhouettes of giant penises, breasts or sticks of French bread. At one point, an evil spymaster sends a secret agent to steal the popularity of Machiko's maicchingu. (We later learn that he's merely the head of a rival school, which disappointed me. It would have been funny if he'd really been Ernst Stavro Blofeld.)
Machiko-sensei has various unfortunate accidents and incidents. At one point she agrees to do a striptease for her class, because that's her only way of getting through to two problem students. (I never had teachers like that when I was at school.) When she eventually performs as promised, two girls in her class enjoy it so much that they ask for stripping lessons. They end up doing a three-girl striptease together for the rest of the class. The finale is a public contest between Machiko and her exhibitionist secret agent enemy, Michiko, with each round's winner generally being the one who's indecently exposed herself.
"I believe that healthy perviness is the road to world peace," says Machiko-sensei, which explains a lot. (She's chaste, mind you. No action. Just flashing.) Occasionally she remembers to wear underwear.
The perverts aren't too bad, since they don't do much. There are a few childish incidents, the most offensive involving a mirror and girls' skirts, but I'd been expecting worse. The most distasteful character is actually the school headmaster, even though he doesn't actually do anything at all. What's bad about him is that he's an older man in a position of power over Machiko-sensei, yet he'll openly lech over her and talk in a way that's basically sexual harassment. Meanwhile Machiko's pupils are older than in the anime, being junior high school students (played by actors who look anywhere between 18 and 35).
Then there's the acting. This is amazing.
Broadly speaking, the men are better than the women. This is because the latter tend to be non-acting models who at most only acted in two or three films, all of them sleazy straight-to-video nonsense by Minoru Kawasaki. Machiko herself is played by Kaori Nakatani, who drifts through the film in an amiable void of anti-acting. She's convincing, as far as it goes. At least Nakatani's Machiko seems like a person, not a fiction created by a bad actor. However Nakatani only has a narrow, bland emotional range and is only really capable of being nice. She's also amazingly bad at strip-teases.
Opposing her, though, is a tsunami of overacting. Misaki Natsuha (?) made my eyes explode as Akita-sensei. She's playing every line as broad as the English channel, but never with even a scintilla of inner life. She's like a low-budget CGI version of herself. She's ludicrous, but after a while my brain sprung a leak and I started looking forward to her appearances. Meanwhile the men are actually okay and mostly succeed with their overacting (although I was put off by Kazuyoshi Miura as the headmaster), while Megumi Aso is by far the best actress in the cast and actually makes it up to "not very good".
They look right, though. From a purely visual point of view, this film is well cast. Nakatani has the right-shaped face for Machiko-sensei and it doesn't matter that her boobs aren't huge. Machiko's never were either, despite what you'd think from the dialogue. Similarly Misaki has exactly the right pinched face for Kyoutou-sensei, although technically she's a new, younger character called Akita. (Kyoutou-sensei was in her fifties or sixties.)
Is this a good film? Obviously not. It's trivial and not even particularly interesting. It's certainly not sexy, despite all the nudity. (That's in common with the source material too.) The only way to watch it is as self-aware absurdity, which in fairness probably is part of what's driving it. This is Minoru Kawasaki, after all. The Maicchingu Music Videos make no sense on any other level, while I had to laugh at Masakazu Migita (Yamagata-sensei) twice falling under a van in a way that anywhere else would be gore comedy. There's no blood, but you can clearly see a dummy getting crunched under the speeding vehicle. The guy should be dead.
It's a live-action cartoon. Kawasaki's finding some unusual ways of doing that, but "unusual" doesn't necessarily mean "good". I'd suggest not watching it, unless perhaps you're drunk.