When someone purposefully sits down to watch horror anime, they should know what they're in for. The same isn't necessarily true for viewers of shows like Yu-Gi-Oh! and InuYasha. Despite being thematically dissonant, anime that aren't typically classified as "horror" contain some seriously freaky scenes.
When classifying the scariest moments from non-horror anime, it's important to decipher what scares people the most. If they're freaked out by existential horror, Joseph's backstory in The Ancient Magus' Bride might haunt them indefinitely. If it's animal cruelty that makes them shudder, the moment when Dio incinerates a dog in JoJo's Bizarre Adventure might be the scariest thing they've ever seen. Meanwhile, Barefoot Gen's depiction of human suffering following an atomic bomb drop is hard to dismiss, since it's based on real events.
These moments aren't simply personal or garden-variety phobias; instead, these scenes are universally unnerving.
It's impossible to discuss horrifying anime moments without bringing up one of the most awful scenes in Fullmetal Alchemist: Brotherhood. There are few scenes in anime as demoralizing as having to endure the treatment of both Shou and Nina Tucker.
Shou Tucker is a state alchemist who made a name for himself by creating a so-called "talking chimera." To retain his position, he had to come up with another wondrous discovery. In one of the most vomit-inducing episodes of the entire series, viewers learn that Tucker will go to terrifying lengths to achieve renown. The first chimera was actually a fusion of his wife and a dog. This miserable creation begged for death, but he still does the same thing to his young daughter Nina, fusing her with a different dog.
When Ed and Al discover this, they're justifiably horrified, unsure of how to respond to Nina's plaintive pleas for them to play with her.
Puella Magi Madoka Magica is known for being a particularly dark take on the magical girl genre, but that wasn't always the case. When it was first released in 2011, many people didn't realize it was going to get quite so intense. After Mami's death in the third episode, all expectations of a Cardcaptor Sakura-esque experience were dashed.
The battle between Mami and a particularly dangerous witch starts off by allowing viewers to feel confident. Mami thinks she can win, and Sayaka and Madoka cheer for her. The witch gets close, Mami's expression changes slightly, and it rips off her head. The manga version of this is even more disturbing, actually showing Mami's half-digested remains.
Barefoot Gen explores life in Hiroshima during World War II. With a premise like that, one could probably assume things aren't going to be peachy. The anime contains many heart-wrenching and terrifying scenes, but the worst is when the atomic bomb is dropped on the city. Instead of simply depicting the explosion and then panning away, this scene dives right into the human suffering and carnage created by the bomb. Skin peels off and eyes dissolve in their sockets, and people try desperately to escape, to no avail.
What makes this scene even more horrifying is that it's historically accurate. This is something that actually happened during World War II, and Barefoot Gen forces its viewers to reckon with that fact.
Princess Mononoke has a number of horrifying moments, but one of the most visceral is the opening scene, where Nago the boar god is on a rampage. After being transformed into a demon at the hands of Lady Eboshi – who shoots him to build industrial developments on the god's territory – Nago blindly rushes through the outskirts of a populated village. From an emotional perspective, Nago's terror and fury are palpable, and it's mirrored by the villagers' desperation to escape him.
Visually speaking, the demonic curse is horrifying to behold; the god's flesh is melted and rotten, and he's covered in writhing worms. The purpose of this disturbing scene is to highlight the consequences of human development in the natural world, and that makes it even harder to swallow.