- Iemitsu's unhealthy obsession with Skeleton Motif. It gets to the point where he goes to battle sites to collect dead human skulls.
- The fact that some of the characters' routes promote blatant Romanticized Abuse, which we're supposed to take as happy endings.
- Genpaku's trying to dissect others at every opportunity he gets, all For Science! One wonders why he hasn't gotten a restraining order.
- The way Mitsuhide always grins when his special skills are executed when the team is low on HP. Hell, the man himself is essentially walking nightmare fuel.
- Sōseki's behavior, which includes trying to jump from the roof of his house and asking the heroine to eat him. He is mighty lucky he's still alive.
- The fact that the one taking care of Shikibu and to whom Shikibu is fiercely loyal to is an all-around creepy Yandere of disturbing proportions makes for some first-grade nightmare fuel.
- Ikusa's being a perpetually warring state. One can only imagine what constant violence and bloodshed with little to no room for peace will eventually do to the lives of its inhabitants.
- The fact that being completely consumed by a shikigami results in Cessation of Existence.
Nightmare Fuel / Akanesasu Sekai de Kimi to Utau