What is the name of a manga about a man with a mental condition that affects the way he sees things?

It was a originally a manga but has now been made into a video game. The main character is a young man with a mental condition that affects the ways he sees the world. To his senses, everything beautiful is ugly and everything ugly is beautiful i.e his bed linen looks like rotting organs. In this world, he meets and falls in love with a beautiful girl wearing a white dress (In reality, she is a grotesque monster who eats people).

The video game had multiple endings, one of which involves the girl/monster populating earth with her own species. Everything becomes beautiful in the man's eyes and they live happily together.
Asked Dec 27, 2013
Edited Dec 27, 2013

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