This film is neither a prequel nor a sequel to the previous year's Kuchisake-onna. Don't believe any idiots (wikipedia) who say otherwise. It's just another story about the same figure from Japanese legend, completely unrelated to any other.
It's also very good, until the last 15-20 minutes when it tries and fails to become a horror film.
HOW TO MAKE A KUCHISAKE-ONNA: (a) become female, (b) get a knife, (c) slit open both your cheeks, from mouth to ears.
HOW TO MAKE A KUCHISAKE-ONNA (IN THIS FILM): be a completely nice, normal schoolgirl for the first quarter of the film. You fancy a boy. You're not beautiful, but you have best friends and a fantastic smile. Then things go bad, then worse, then ultimately... well.
The film's first 25 minutes are charming. It doesn't feel like a horror movie at all. We meet Mayumi (played by Rin Asuka), her sisters and her parents. Dad's a chicken farmer who's a lovable chap but not much smarter than his flock. Goodness knows how he managed to marry a clever wife and raise three smart daughters, but he did. Anyway, the film fits a lot of character and charm into that first act. I paused it for something after twelve minutes and was surprised to learn that so little time had passed. I'd have sworn we'd had a good twenty minutes worth of film. Mayumi rejects a boy's love confession, gets frighteningly bad boy-chasing advice from a well-meaning schoolfriend and gets comedy music as she tries and fails to get closer to her crush, Seiji (Akihiro Mayama).
It's a gentle, likeable film about normal people. Mayumi's sister Sachiko is getting married, while her other sister Yukie is working at a hair salon.
Then the bad thing happens.
It's extremely bad. What's worse still, though, are the reactions. People in town start swapping rumours. They all stare at Mayumi on the bus. Her classmates go from "nice" to "vile" to "I wanted them dead". Seriously, stuff like the blackboard graffiti is unforgiveable. Of all people to bully, why Mayumi? You'll notice that she's permanently self-conscious after that about their nasty throwaway comments.
This is completely different from the film's good-natured first act, but it's equally well done. By this point, I was thinking I'd found a hidden gem.
Unfortunately the film's been building up to a last act of horror. On paper, it's fine. Nothing wrong with it. Strong character decisions have horrible consequences. Sounds great. The problem is that the director, Kotaro Terauchi, doesn't know what he's doing. Understated slice-of-life charm, yes. Grand guignol, no. There's a huge turning point that makes everything irreversible and should have been the film's electrifying dramatic height. It flops. The actresses are bleah and the director's giving the scene no oomph. After that, we have a laughable reaction shot to the gore at the hairdresser's and a night-time kill where you can see sunlight shining through holes. Theoretically it's still a strong finale, but the execution is limp. I didn't even like the music choices.
Even then, though, was the film's approach to its supernatural content. The traditional kuchisake-onna is undead (variant unknown but very bad), but this film appears to be entirely real-world almost until the very end. If one assumed a subjective viewpoint shot or two, it would be possible to read the film as containing no supernatural elements at all.
I liked the cast. This was the same year Rin Asuka played Mion Sonozaki in the first of her two Higurashi live-action films, incidentally. (NOTE: those are the good ones, not the somewhat laughable 2016 live-action TV series.) She's good here too. I like Asuka.
Overall, despite walking off a cliff at the last minute, this film is very good. Most of it is great. Its last act is poorly done, but I'd recommend the film anyway. It can be shocking, and not in a horror-movie way. The creepiest thing about it, though, is this opening. "This film is based on actual events which took place in Gifu in 1978. Names have been changed to protect the victims' families. The case remains unsolved." (I don't know which bits of the film they're talking about or to what extent they embroidered things, mind you. There's more information at the end credits, but it didn't tell me what I wanted to know.)
The Slit-Mouthed Woman is turning out to be a fascinating horror franchise. She's so nebulous that you can tell all kinds of stories around her.