In the world of the humans, demons live in the shadows. There were demon hunters so not many demons were left, and Rui was one of those demons left. He creeps in the shadows and haunts humans in revenge. But, he has a silly little best friend, Tsukasa. Tsukasa was the angle to his demon side and kept him out if trouble a lot. Currently, Rui was stalking a demon hunter at night, ready to kill him.