Ouri is an orphan who was raised by Keisei, a man he considers to be his older brother. One night, Ouri finds a strange wounded girl in the temple of the orphanage. Cold and covered in scars, Ouri initially thinks that she is dead – that is, until a mysterious talking cat tells him that she is a Shikabane – a corpse. After secretly watching Keisei heal the girl without explanation, Ouri decides it's time to leave the nest. However, he has picked a poor time, and he soon realizes that he's tangled in a strange, supernatural web. Why does Ouri continually meet this girl as she hunts monsters? What does Keisei have to do with it all and what exactly is her mission?