It's a horror film. The 2016 anime series was going for laughs, but this is playing it straight. Alas, I preferred the comedy. I got through this film and it has its moments, but it's forgettable and I'd expect even a horror fan to give it only about six out of ten.
The premise involves a computer game called Ao Oni, in which teenagers get hunted and killed by Ao Oni. (He's a big blue demon.) That's both in real life and in the fiction. This film is adapting the game, but its characters are also telling each other about the game and organising interviews with its author. They're high school students investigating a legend that's reminiscent of Ao Oni and it turns out that the computer game was created by someone from this town!
The animation's bargain-basement, as usual with modern horror anime. We're just lucky that the running time's longer than three minutes. It's blatantly computer-built, of course, and cheaply too, but in a different style to that in its comedic 2016 predecessor. The style's more realistic. Nonetheless the computer models are unsophisticated and come across like Thunderbirds puppets. A supposedly sexy woman just looks like a plastic doll. This doesn't help the horror, obviously. If I hadn't been able to hear the voice actors, my viewing experience would have been as dead as a doornail.
The film's first half is all committee meetings and investigation. Our heroes explore the school, learn that it has a suspiciously large basement and talk to a former student from the 1970s. It's all pretty dull. The characterisation is bland and the dialogue is placefiller. You'll be disappointed that no one's being eaten. Nothing here is good or interesting, although it's not bad enough to make you turn off the TV in a rage either. If you're feeling generous, it's scraping the lower end of "okay". The situation is being presented coherently, the characters' investigation of it makes sense and they're making progress towards their goal of uncovering the truth. In practice, though, this mostly means talking. They talk. Then they talk some more. They explore the school. It's a bit dreary. Some of the detective work isn't bad, I suppose, and I liked the glimpses we get of how things were different in 1976. Our heroes have to work out how to play some open reel tapes, for instance.
Eventually, though, of course, Ao Oni starts killing. This happens at a suspiciously exact time. I'm not a fan of anime films that, say, have their big fight start at exactly the 60-minute mark and continue for exactly 15 minutes. Call me a silly old buffer, but I like to think that story beats should unfold naturally rather than because everyone took the director too literally when he said, "This film will be an hour long and we'll have X happening halfway through."
That said, though, it's more entertaining with Ao Oni around. Our heroes come up with some intriguing hypotheses about why Ao Oni might be on the rampage, although the eventual explanation is even wackier. That was quite fun. The film ends reasonably well. As for the gore scenes, they're way too dark (the last resort of cheap CGI), but the film's not trying to dodge the freakiness of a giant smurf who likes biting heads off and there's one genuinely creepy bit.
It's still not good, though. There are a couple of credibility-straining bits in the second half, once when two members of the fairly small cast turn out to have a hidden connection to the events of 1976 and then later there's a bit in a climactic scene where Ao Oni gets put on hold or something. There's a long-ish conversation and it's as if we're meant to forget that there's a monster standing there who's trying to eat people. Overall... this film reaches a basic competence threshold in that its story is too straightforward and its characters too drab to be doing anything particularly wrong (if you don't count the visuals) and it's passably watchable in a "hey, it's only an hour long" way. However a kind description would be "uninspiring". I'm still planning to watch the 2014 live-action film, but I've adjusted my expectations.