No one is safe in this story and no one gets a good ending.
Fuminori Sakisaka is a young medical student whose life changes when he and his parents are involved in a car accident. Fuminori is the sole survivor, but sustains a head injury that requires brain surgery, after which he develops a severe and bizarre case of agnosia that permanently affects the way he perceives his environment - the world appears as an abominable hellscape covered in gore, humans look like monstrous lumps of flesh, spoken words sound like grunts and screeches, normal meals taste and smell repulsive, and his sense of touch is impaired. Fuminori contemplates suicide until he meets Saya, a small, cute girl in white who's looks drives the average onlooker to panicked madness for mere childish pleasure, but is amused by the unflinching, if now hopeful, Fuminori. Fuminori, desperate to make contact with anything that resembles humanity, and Saya, amazed by Fuminori's reaction to her, become lovers and move in together, eventually becoming deeply dependent on one another, with Saya in particular wanting Fuminori's help in finding her missing "father," Professor Masahiko Ogai. While living in Fuminori's home, the pair covers the walls and windows with random coats of paint of varying colors to attune to Fuminori's vision, while Saya acts as though she is Fuminori's wife, doing her best to cook and clean for him.