Fortune Is Unpredictable and Mutable.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. Dazai and Kunikida explain that they are searching for a tiger that has been ravaging warehouses and livestock. Atsushi states that the tiger had been following him throughout his traveling, and ends up posing as the bait to help the two agents capture it. Dazai slips Kunikida a note and takes Atsushi to a warehouse. Atsushi explains how he was kicked out of the orphanage to save money, because the tiger had caused the financially poor orphanage a great deal of damage. Dazai concludes that Atsushi is the tiger, or rather that he has a supernatural power to transform into the tiger under moonlight. The full moon is revealed and Atsushi transforms and attacks Dazai, who reveals his special ability: "No Longer Human", which stops all other abilities when he touches a person. He is able to subdue Atsushi. Not long after, Kunikida arrives at the scene with three other agents. Dazai decides to make Atsushi a member of the Armed Detective Agency.