Saya no Uta

The story centers around Fuminori Sakisaka, a medical school student involved in a vehicle accident that claimed the lives of both his parents and left him with critical injuries.
He was rescued by experimental brain surgery that coincidentally altered his perception of the world dramatically.

Everything now seems to be composed of slimy intestines and gore to him. In addition, the rest of his senses: touch, hearing, smell, and taste, are also impaired, similar to his sight, further damaging his mental health.

Fuminori's desire to live dwindles, and one night, while still in the hospital, he contemplates suicide. However, a girl in a white dress named Saya appears before him. Compared to the horrible surroundings, she looks completely normal, if not downright gorgeous. Fuminori soon falls in love with Saya, and she becomes his raison d'être.

As time passes, Fuminori gets increasingly secluded from the rest of his normal life as he embarks on a mission to find a specific person Saya is looking for. Fuminori's friends and doctor get more concerned as he acts strangely over time. Nonetheless, they will soon cross paths, for better or worse...