Since the age of seven, Tatsuki Kawamura was a loner with an uneventful life. But one day, one a school field trip, Tatsuki is thrust into a world where he can see animals -and people- become possessed, and a saber-wielding girl is his only chance at regaining sanity. The girl, Misaki, promises that she will teach Tatsuki his birthright as a Ryuu- a class of supernatural-fighting warriors who have existed for thousands of years in secrecy.