It's timid sexploitation. Sometimes it's recognisable as a film, with a story that's happening to the characters. Sometimes, though, it's just a slice-of-life look at their day-to-day routine (i.e. a big pile of nothing), in a way that might have been intended as either "sleaze" or "comedy".
Unfortunately the film fails hard on both counts.
The first half-hour is just geisha entertaining their clients. For what it's worth, onsen geisha were regarded as the lowest class of geisha and closer than others to prostitution. (This film fudges the distinction. There are traditional geisha arts like singing, music and dancing and they resist being called prostitutes, but there's clearly some adult-only entertainment taking place. There's boob-sucking, dropped bras and a bottle of stage blood in order to fake virginity. Some of the geisha do say "no", though.)
It's a contemporary film, by the way, not a historical. The music and dancing especially shout "1960s".
This is boring. It's a bunch of shuffle-and-forget scenes that add up to nothing and go nowhere. Sometimes you'll have everyone together in a room and the girls will dance. Sometimes you'll have a man (in his fifties) and a woman (in her twenties) together in a room, playing out a brief, pointless scene. Maybe it'll be attempted comedy. Maybe it'll be mildly surreal, e.g. a priest telling a girl that you've got to be naked to pray to Buddha. It'll usually have no sexual content at all, e.g. just a massage, but even the suggestive scenes aren't sexy. The girls wear huge, old-fashioned knickers and occasionally strip in a way that carefully hides everything, while the camera stares from a distance in a blank, dead-eyed way that suggests the director wanted to shoot twenty more scenes before lunch.
Admittedly the girls seem to be having fun. They're lively. However they're also bitchy, capable of sabotaging their colleague's singing performance or of having an actual fight for no apparent reason beyond mean-spiritedness. The nastiest example is much later in the film, when they have to be talked down from roughly pushing around a woman who's recently given birth. (Yes, she stole money and abandoned her baby, but even so. Yowch.) Meanwhile their clients include one section chief who pulls faces as if he's been watching too many Carry On films. He could have been funny with better material, but this is not that film. (I liked Buck-Toothed Bloke, though.)
After too much time, the film starts trying to grow some plots. It does so in episodic, fragmented ways that play out like short stories that aren't connected and ultimately wind down all by themselves, but that's still better than before. There's a man who's run away from his family and calls himself a dropout and a failure. There's a stone-cold doctor who takes an aggressive lack of interest in a girl who's interested in him. There's that pregnant woman I mentioned. The film's biggest (albeit short-lived) leap in quality is when someone dies.
There's also a long scene when the film breaks its rules and shows boobs. All the girls get in the hot spring and have a cat fight. Meanwhile a peeping tom's hiding in the bushes with a film camera, for added unpleasantness. All this is shot in the same unflattering, bored way as the rest of the film's naughty content. (There's only one exception to this rule, much later, in a scene where a girl's top is hanging open.)
You'll be interested to learn that childbirth takes only a few seconds and doesn't seem to hurt, even though the baby we see is huge, strong and clearly several months old. Another scene has a crying baby on the soundtrack, but a completely calm baby on-screen.
This film has a few good scenes, but they're rare and easily forgotten. I liked the quietly sadistic scene where the geisha receive their pay, for instance, rubbing in the declining fortunes of a girl who used to be number one. I also liked the scene with the daughter of the man who died. Ultimately, though, this is a bits-and-pieces film that feels as if it's been roughly edited together from unrelated flicks. Great chunks of it are worthless. Sometimes it's competent filmmaking, but only sometimes. It feels like an attempt at a sexy film for boring people who couldn't have handled anything actually sexy.
There are at least six of these Hot Spring Geisha films. That's five films I won't be watching, then.