To be honest there’s likely a better place to put this, but this is a unique enough piece that I felt it deserved its own thread. Saya no Uta (Song of Saya) is one of THE most famous horror visual novels of all time and was one of Gen Urobuchi’s early works (2003, years before Madoka or Psycho Pass). It’s pretty infamous for its grotesque imagery and haunting soundtrack.
The synopsis is simple: a med student gets into a car crash where his parents die, and is saved by an experimental brain surgery. It has the unfortunate side effect of warping his perception of the world, making him see, hear, touch, and taste everything as being made up of rotting flesh, filth, and decay. Everything except for one person: a girl named Saya. As she is his last link to sanity, he vows to reunite her with her missing father while growing ever more distant from the ones he called friends.
I’d say more, but it’s a very short work that relies quite a bit on surprise (and on the off chance anyone wants to read it, spoilers abound on the Web.) It’s one of the rare Terran horror stories that don’t rely so much on the physical threat of harm to scare or unsettle the audience. Gen himself has said it was inspired by reading Lovecraft, and there are strong existential and cosmic horror overtones.
The main squick for eldrae: It’s implied that the brain damage has reversed the protagonist’s sense of aesthetics to such a degree that he can no longer appreciate any kind of beauty, and he doesn’t see Saya for what she really is. It’s all but stated she is some kind of unspeakable eldritch monstrosity ala Ghatanothoa.