Nakajima Atsushi, a starving, homeless orphan, encounters a man floating down the river who appears to be drowning. Atsushi dives in and rescues the man, who comes to consciousness and introduces himself as the suicidal maniac, Osamu Dazai. Dazai's colleague, Doppo Kunikida yells at Dazai from across the river and ends up treating Atsushi to a meal of chazuke in a tea house. Atsushi discovers that Kunikida and Dazai work for the Armed Detective Agency, an organization of individuals possessing supernatural abilities...