Nakajima Atsushi was kicked out of his orphanage, and now he has no place to go and no food. While he is standing by a river, on the brink of starvation, he rescues a man whimsically attempting suicide. That man is Dazai Osamu, and he and his partner Kunikida are members of a very special detective agency. They have supernatural powers and deal with cases that are too dangerous for the police or the military. They're tracking down a tiger that has appeared in the area recently, around the time Atsushi came to the area. The tiger seems to have a connection to Atsushi, and by the time the case is solved, it is clear that Atsushi's future will involve much more of Dazai and the rest of the detectives.