Nakajima Atsushi was kicked out of his orphanage, and now he has no place to go. He rescues a man who 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. Atsushi's future will involve the ADA.