Okay, let's try this in a way that's not too disorganised.
Summary: As a movie, I think it's solidly decent, and I'd probably have enjoyed it in its own right. As an adaptation of Otsuka's novel, it's a masterpiece. "Adaptation" feels like the wrong word; it's more like a renovation. Somehow everything is recognisable, and yet everything is improved. I was actually worried from reading reviews that Asato had kept too much the same, but by the end everything hung together, and it worked.
If you have read the novel, let me reassure you now. There is no menstruation talk. There is no spongebath scene. There is no powerpoint exposition.
Getting onto the specifics, I think I'll attempt to divide this up into categories.
The characters are a resounding improvement. All of them feel real and human in a way they never did in the novel. They might be outsiders, or in a difficult stage of life, or suffering from confusing feelings, but there's none of the sense that I got from the novel of people drifting along as if watching it all through the lens of a camera, with a sense of vague disgust for everyone else frothing just under the surface. To me the novel was claustrophobically misanthropic as well as misogynistic, kind of like the whole thing was narrated by Taruho, but the movie was refreshingly kind to its characters. Mari Asato seems to have a much better grasp of what it's like to be a teenage girl than Eiji Otsuka, too. (I know, what a shocking revelation.)
For specifics... Mary was an odd woman, a little misplaced in the town, but not portrayed as desperate, pathetic or fake, and she doesn't have to give up her frilly clothes at the end. Likewise, Susumu is an odd kid, but there's not the same unpleasant friction between them as the book. Mayumi's feelings for Takashi are still clearly not quite right, but her concern for him is genuine, not purely selfish, and the weird incongruous axe-killer stuff is gone. Michi is my favourite, and the most changed - no eyepatch, no hatred for her parents and the idea of romance, no inconsistent psychic ability, and best of all, no obsession with menstruation - but I liked Aya very much too. She had a lot more agency, and the sense of her strength and determination really come across through her actions, rather than just someone telling us about it. In the book it seemed like she was getting pushed around like a pawn and objectified for 95% of the time, sometimes voluntarily (by allowing herself to be cursed), but in the movie nearly all of that is gone, and most of her actions originate with her own decisions.
Which brings me quite neatly to Karatsu and Makino. Take note, Otsuka, when most people say "cameo", this is what they mean. They show up for about two scenes, and although they help save Risa and move the plot along a little, they don't know everything. In the novel, nearly all of the relevant plot exposition comes through them or their mouthpiece Ritsuko (who's not even in the movie AFAIK); in the movie, hardly any of it does. Most of the cast have little pieces of the puzzle, and it all comes together in stages at the end, which feels much more balanced.
Story and Scares
Big big big improvements here. Again, the skeleton of the plot is the same, but a lot of fat is trimmed and a lot is simplified and makes more sense. Especially about the curse. As for scariness... I wouldn't call it scary. It's eerie in places, and there are a couple of points where Ayami Nakajo as the ghost really does seem spooky, but as that reviewer on Kotaku said, it's more about building a particular atmosphere than giving you nightmares. Personally I live for atmosphere, so I liked it, but I can see why people would feel let down.
Since it's quite a significant element in both novel and movie, I'll also say a bit about f/f relationships here. Sexual and gender politics in Japan is a big old complicated thing that I can't even begin to unpack, so I won't try, but I will say that even though there's less onscreen f/f in the movie, it felt a lot more respectful and a lot less voyeuristic. I think the biggest change was to yuukon. In the novel, it was a ritual for men and women, and the problems started when it got repurposed by schoolgirls expressing their confused adolescent feelings. In the movie, it was for women all along, women who were in love and felt they had no other choice. The events are much the same, but I think you'll agree the implications are different. As for further interpretation, I'll leave that to someone more qualified.
Not much to say here. The film was beautiful. The settings were perfect and used well, the casting was great, the camera work was lovely.
As a Fatal Frame movie?
I think the main thing a lot of people on this forum will be worried about is how it stacks up specifically as a movie with the Fatal Frame title. I think I'm going to have to qualify my thoughts on this a lot, because on the surface it's quite different, even more so than the novel. The novel did at least have a shrine (albeit one rebuilt in modern times), and the Camera Obscura actually appears less in the movie than it did in the novel. There are still no ghost fights, no ancient or abandoned buildings.
But to me it felt like the movie understood the themes of Fatal Frame far better than the novel. There's a sense of sympathy for the characters trapped in such difficult situations, and how for the most part their actions are driven by fear or desperation rather than mindless cruelty, even if they aren't the actions we ourselves would choose.
And there's a sense of history, even if it's only touched upon. The section I'm thinking of is when Aya and Michi visit Mary at her house, which is also a photo studio. She takes them to a room where all the yuukon photos are enshrined behind sacred rope, and several old cameras are on display. (This replaces the shrine and the Ophelia Album from the novel, and after my initial disappointment about the loss of the shrine, I like this better.) There's a flashback to the man we know as forearms taking a picture of two young women dressed in old-fashioned clothes. The women then kiss each other's photos and proceed to drown themselves in the lake. We never find out who Forearms is, or who the women were, or how this practice got started in the first place, but if you're a fan of the series, I think the gaps in our knowledge are much more suggestive than Makino telling us all about the history and origins of yuukon in a very matter-of-fact way. It really feels like this is a story that could take place on the fringes of the Fatal Frame universe, and it wouldn't take much to bring the two together in a more substantial way, which is all I really wanted.
But I won't lie, if you're looking for lots of camera folklore and exorcisms, you'll probably be disappointed on that score. The emphasis is all on interpersonal relationships.
To close, here are some random thoughts that didn't fit anywhere else:
- Hooray for Aya getting her own memories back without any intervention from crossover characters!
- Michi having actual friendships with people! I was really touched by her attempts to keep Risa from being spirited away, and her genuine distress over Kasumi's death.
- I do wonder what would have happened if one of the cursed girls had managed to reach the water tank.
- I think the only plot changes I slightly regretted were the ones to Mio Takaishi and the Headmistress. I quite liked Mio Takaishi's relentless vengeful rage, and the curse of immortality. But I can accept it, since it doesn't really fit the tone of the story the movie is telling, and I do like that the Headmistress is visibly upset, not "expressionless, as though nothing had happened", after she can't go through with suicide.
- The cast are just the most charming girls and I hope they have wonderful careers ahead of them. But the breakout character was Background Duck.
- Mari Asato for president.
Let's see how stupidly tl;dr this is.