It's really weird. Most anime fans seem to agree that it's badly written and that the characters are awful, even when they go on to say that they couldn't stop watching every week. There's a fascinating article on Anime News Network that calls it a comedy about subverting genre and deliberately breaking our conventions of telling drama, especially horror. In short, it's controversial. Discussion of it would often be about whether or not it was intentionally bad. It's not an easy show to process. It's full of idiots, episodes are liable to get clogged up with interminable discussions that go nowhere and even I found the middle episodes dragged a bit.
I think it's impressive. You'll need a bit of endurance to get through it, but I think it's brave and successful (in a slightly awkward way). The main thing you'll need to do is to discard your normal relationship as a viewer with most of the cast.
It starts with thirty people on a bus. They've all agreed to reject civilisation and discard their old lives, instead going off to live together in an abandoned village in the mountains. They did this because they received an email.
It's hard to know where to begin... no, actually it's not. They're idiots. They've self-selected for reality-resistance. One of them has a weak constitution and needs to take medication, so he clearly wasn't thinking deeply. Another is always demanding that someone be tortured or executed. (She doesn't seem to mind who it is. She just likes executions.) There's an obnoxious guy who couldn't be polite to save his life and does things like kicking the back of the bus driver's seat while they're moving along. There's a girl who says she's here just to try to get a man. (Your options aren't great, darling. One of your new friends just got out of prison, for instance.) Not all of them are idiots, admittedly, but the ones who aren't will instead be psychologically damaged.
Almost no one here will have known anything about anyone else, except that they're the kind of people who'd sign up for something like this. Would you want to spend a weekend trapped in the mountains with these people? No. Well, everyone here signed up for the rest of their lives, with no access to doctors, dentists, opticians or any of those other pesky burdens of civilisation.
Obviously it seemed obvious that the show was going to be a bloodbath. You don't front-load this many speaking characters unless you're about to start killing them off, especially in an anime from the director of Another. I could tell what the show was going to be... but I was wrong.
It's not a horror show. There's no bloodbath. It's imitating the structure and form of psychological horror, but it's something else.
Psychological it certainly is, mind you. However it was a bit of a struggle to keep watching when the group was having stupid discussions that went in circles and seemed designed to attract the most ridiculous arguments. Put these people in a group and you'll start a chain reaction of stupid statements springboarding off each other until the group is thinking in ways that you couldn't imagine for a single human being. Sometimes this is just tedious. You want them to shut up. Later, though, you realise that the show's saying something much darker with this when the group convinces itself that one of their number is a ghost and so they have to kill her. If she is a ghost, you see, she won't die and they'll be proved right! You might have spotted the logical flaw.
In short, they're the internet. They're what happens when people get together and their group-think spirals away into irrationality. These people will start nitpicking your statements and asking why you didn't do this or that, ignoring the fact that you're emotional and that you're not a robot. They're idiot fanboys dissecting the world with intellectual tools they don't know how to use... or at least that's my interpretation. I'm lucky. I live in a society where the internet is the best model for this kind of group behaviour. Unfortunately there have been many times and places where that kind of thing happened for real, in ways that are deeply scary.
The show's a study of that. From that viewpoint, the huge cast makes perfect sense. It's not just a bait-and-switch to set up false horror expectations, but a necessary precondition for being able to portray what people can turn into when they stop thinking individually.
And then the show changes again... and I can't go into detail here because that would disembowel the show. However what it's doing is turning the spotlight back on those individuals and the fact that they were basically rejecting themselves by coming here. It reinvents empathy. As everyone here is demonstrating, it's so easy to believe that you're the only one who's hurting and that everyone else is happy and perfect. Their enemies are the parts of themselves that they'd rejected. There's a weird supernatural reflection of one's inner life that ties in with the Lost Village and turns the entire show into a metaphor.
The Lost Village itself is a clever story ingredient, by the way. (It's like the Mary Celeste, but as a village in the mountains.) It's weird enough to be wrong and magical, yet also (in Japan) plausible enough to be taken at face value. Villages are indeed being deserted as the population ages and the young people all leave for cities.
The cast is full of obnoxious nutters, but also enough likeable people to make me care. That said, though, even the hero (Mitsumune) is showing us the dark underbelly of the all-trusting super-nice anime hero. Mitsumune is a sunny, upbeat chap who'll always believe you, no matter what you say. He'll stand up for the underdog. He'll take your side. He doesn't need to listen to the facts and he won't reject you even if you admit flat-out that you've been telling him lies. In this environment, with these fellow travellers, this makes him a mildly dysfunctional thematic mirror of... um, certain other people.
You might be wondering what he's doing there. Well, let's just say that he falls into the "damaged" category. There are some pretty horrible backstories here, although the narrative's not just wallowing in their tragedy. The focus is on what these people do next. What will happen if they accept their trauma, or else just reject it and try to shut it out? How many will be willing to return to reality at the end? Not all of the messages being sent here are comfortable.
Is this show mental? I don't think so. It's brave. It's deliberately doing things that made the audience think it was badly written. It's playing with genre expectation and putting up neon signs saying "THESE PEOPLE WILL DIE LIKE FLIES", only to turn around and kick our legs out from under us. I wouldn't call it a comedy, but it does occasionally make black humour from these people's bad behaviour and expectations. I laughed at little moments like someone holding out their arms for an embrace (sorry, mate) or the minor running motif of people vomiting on you. Not all of the cast are equally developed, of course. I was mildly irritated by the one-dimensional Dorky Fat Guy. However if you see complaints about all the stupid characters in this show, that's a feature, not a bug. That's the point. That's part of what the show's examining, although there's far more to its themes than that and you'll confuse yourself if you try to flatten everything into an Internet Fan metaphor. In the end, I found it fascinating.