That was sometimes hard to watch. I'm not even halfway through the franchise, but for a while I was thinking of quitting after Season 1 and never going back. It's worse than ordinary horror. Ultimately, though, we got revelations that recontextualised everything and made me a bit happier about continuing.
It started out as a visual novel, i.e. choose-your-own-route computer games. This explains a lot. The anime's doing something similar. This season has six story arcs, each of which is a complete reboot of the others. They're mutually incompatible, often due to death. Same setting, characters and backstory. Various starting points. Completely different endings, often extremely gross and/or driving the protagonist into insanity, murder, torture or oh my God.
One of the many disturbing things about this show, though, is that the backstory's mostly consistent. Remembering, say, the white van from another route will make the current one more sinister. This builds up an increasingly distressing picture of what's going on.
Here are all 61 "episodes" of the anime:
2006 = Season 1 (26 episodes) = "Spirited Away by the Demon", "Cotton Drifting", "Curse Killing", "Time Wasting", "Eye Opening", "Atonement"
2007 = Cat-Killing Chapter (bonus episode for the Season 1 DVDs)
2007 = Season 2: Kai (24 episodes) = "Reunion", "Disaster Awakening", "Massacre", "Festival Accompanying"
2009 = Rei (5 OVA episodes) = "Embarrassment", "Dice Killing", "Daybreak"
2011-2012 = Kira (4 OVA episodes)
2013 = Outbreak (TV film)
The franchise also has the original games, a 17-volume novel series, a ten-part live-action TV drama (2016) and two live-action movies (2008-09).
A boy called Keiichi Maebara has moved to the village of Hinamizawa. It's in the middle of nowhere. The local school only has about a dozen pupils (all shoved into the same class, regardless of age). Apparently it's the year 1983, but it's the kind of sleepy rural area that could fit into almost any year in the last century. Every route begins with goofy silliness between Keiichi and four village girls: Rena, Mion, Rika and Satoko. It's fun. It's light nonsense, as in a million anime. You'll relax and enjoy it... and then we'll approach the annual murders and disappearances at the time of the Cotton Drifting Festival.
I can't remember seeing anything else like this show, with its variations on a theme of descending into darkness. Nice people go crazy. It would often genuinely get at me to watch a perfectly normal protagonist going ever more unlikeable and stupid.
Fortunately, though, there are eventually some explanations. Stuff ties together that you wouldn't have thought could be linked. Knowing what I know now, I'll keep watching. Things are more understandable. I know some reasons. Stuff I'd written off as too absurd to be true has turned out to have been logical, underneath, e.g. those reports of people who bled to death, alone, while clawing out their own throats with their fingernails. (Mind you, there are fans who reject those explanations as too silly and/or genre-busting.)
It's extreme. I respect that, but it's putting obstacles in its audience's way. For casual viewers, it'll be unwatchable. Even for me, it was hard. It's unique and I'm sure it's revered by its fans, but it sold poorly in the West.
After that, a slight and counter-intuitive problem is characterisation. The show has two extremes: (a) light, fluffy nonsense, (b) a journey to hell. The former makes everyone look like anime bimbos (including Keiichi), while the latter's often plunging too deep into horror to suggest much about what the cast would be like under normal circumstances. Mion/Shion I have clearest in my head. Rena I'm fuzzy on and I think it's telling that the show's fandom tends to exaggerate her questionable psycho tendencies. (Almost everyone goes bad in some iteration of this show, plus of course not everything is reliable.) Satoko is mostly just a backstory, although I know she loved her (late?) brother. Rika is even less clear, but she has layers. I'm not particularly confident about what those are, but I presume finding out will be important.
Rena's the girl who likes the local garbage dump, her nata and repeating the end of her sentences in a verbal tic that gets old fast. (A nata is a sort of square-ended cleaver.) Mion's the green-haired buxom one who SPOILERS SPOILERS SPOILERS, but bloody hell. Satoko and Rika are younger, with Satoko having egg sushi hair and Rika being a shrine maiden.
Keiichi's just a standard anime protagonist, though, which is fine. He's the token male. That's enough.
For what it's worth, the writer (Ryukishi07) was influenced by Key visual novels like Kanon, Air, Clannad, etc. He thought they were brilliant, so he analysed them. Their trick, he concluded, was to start pleasantly and normally, but then surprise you with emotional content that made you cry. This uses the same pattern, but, uh, eliciting different reactions.
RANKED FROM "AUDIENCE TORTURE" TO "OKAY"
SOD OFF AND DIE = "Spirited Away by the Demon". Obnoxious, hateful and I wanted him dead. Mind you, it also has the shock value of being the first in the season. If I went back and rewatched it now, I might see his behaviour as rational and sensible.
OBJECTIVELY, EVEN WORSE = "Eye Opening". Retells an earlier route from another character's point of view. Has the most disgusting and hard-to-watch content, but I found it easier to take than "Spirited Away by the Demon". We're in the second half of the season and by now I've worked out what to expect.
GYAAAAAH = "Curse Killing". No, Keiichi. Bad idea. Don't do it. I also have no idea what was happening with the ending, but that might become important in hindsight.
HORRIFYING, BUT IN A WAY THAT'S MORE LIKE REGULAR HORROR = "Cotton Drifting". Jaw-droppingly evil and has more of those annoying lies, but at least you don't want to kill the protagonist yourself.
NO PROBLEM = "Time Wasting". A relatively quiet two-parter set in the past.
WELL, I DIDN'T SEE THAT COMING = "Atonement". Has perception-redefining revelations and does something unprecedented with its ending. This was the thread that convinced me to keep watching the show after all.
Hilariously, it's about friendship and trust. (Like PreCure, but different.) There's a demonstrable progression as we move from thread to thread. The character flaws at the beginning come from paranoia, mistrust and lies. By the end, friends are fine with murder and dismemberment, because they're friends.
I'd recommend this show to almost no one. When Tomoko heard that I was watching it, she thought I'd suffered an alarming lurch in taste and common sense, even compared with what I normally watch. (None of her friends watched the anime, but one of them played the game.) Even today, it's still famous. It's strong stuff.
"To the fun, fun underground torture room."