To make things short, the main male protagonist, Fuminori, is a guy who pretty much wakes up from a brain surgery after a freak accident, but finds out that everything around him has the appearance of rotting raw meat. This includes all the people around him too. Apparently everything had become repulsive to all of his five senses, except for things that are already disgusting in reality. In that case, he would find the look and smell of real rotting meat pleasing.
Fuminori thought he was in a real hell, until he met a pretty little girl...
The only person in the world that didn't look like a monster.
This little girl's name was Saya, and she really is a sweetheart
Through the game Fuminori is basically looking for Saya's "father", a mysterious doctor, in order to find out what happened to his brain, and to help Saya look for answers as well.
A lot of people are scared out of their pants from how gory the game is, but the innocence of Saya and the degeneration of Fuminori's humanity are what make this an interesting and bittersweet visual novel. You'll pretty much be on the edge of your seat during the whole game. This is a must play for any visual novel fans, but you'll be disappointed if you expect any happy endings.
Haha my first summary ever （ ´Д｀）;;~
Here's a little doodle of little Saya I did <3