WARNING: Spoilers ahead. Read at your own risk.
Better the assistant you know than the one you don't
Everything about this is in some way or another the stuff nightmares are made of. Some of the more notable examples:- Koishi's flower fortune telling, which involves ripping legs off of a grasshopper. It's not as scary as the other examples, but it's probably the first sign that something will go wrong.
- Koishi ripping out Hong Meiling's throat down to the spine.
- Mokou burning down the Human Village for kicks and giggles.
- Yuyuko eating Youmu, her gardener and most loyal servant.
- Sanae torturing Kogasa and having killed Mystia off-screen.
- Yukari losing Ran and Chen in a gruesome manner while getting curbstomped herself in the most painful way.
- The Nightmare Fuel Coloring Book which is used as the intro of Episode 5 is grossly horrifying and twisted. Even more so after it is revealed that the picture book is a manifestation of Koakuma's inner hatred for everyone and her obsession toward Patchouli.
- Nazrin and Shou getting the death penalty for not sharing Byakuren's madness-induced ideal and refusing to attack humans. Both are beheaded and have their heads impaled on spikes.
- Giant, frenzied Gensokyo residents invade earth and managed to wipe out enough humans to drop the population down to 95%... then 94%... (this means that over 420 million people have already died and it's only getting worse from there).
- The story of the depressed mother. A young Japanese woman marries her boyfriend and they have a baby. Unfortunately the husband gets bored of her and frequently cheats on her, she gains post-partum depression and thinks her baby daughter is plain, annoying and cries constantly. After having a nightmare in which the baby grows up to become a bratty teenager who Really Gets Around and aborted her own baby, the mother snaps and kills her daughter by strangling and submerging her in a bathtub. Koishi (who had been watching over the woman since she was single, as she grew curious on her) is horrified and kills the woman as she's preparing to dispose of her daughter's corpse. How? She possesses the baby's corpse (drenched and with swollen flesh from being underwater) and impales the mother with her tentacles.
- The fact that all of this started from something innocuous, just a simple request to use a fishing rod.
