Nakajima Atsushi, a young man who was chased out of an orphanage, joins the Armed Detective Agency, a group with unusual abilities, after saving Dazai Osamu, a man who was attempting to commit suicide by drowning himself in the water. Soon, Atsushi's abilities are revealed, and he joins the group, including the feared Akutagawa Ryunosuke. Confrontations with the Port Mafia and the North American Psionic Groups and Guilds intensify.