Port Mafia leader Mori Ougai orders a fifteen-year-old Dazai Osamu to investigate the appearance of a certain individual in the Yokohama Settlement area.

Nakahara Chuuya and Dazai Osamu reveal the truth behind Arahabaki, Randou, the former Port Mafia boss and Chuuya himself.

The Agency is tasked with finding and delivering an important document. A man is hit and killed by a truck. His identity shocks Atsushi.

The leaders of the Port Mafia and the Detective Agency are attacked by an assassin in a mask, leaving both of them ill.

Mori Ougai and Fukuzawa Yukichi fight to the death in a desperate bid to save the organizations they lead from falling into a devastating war.

Security police officer Fukuzawa Yukichi arrives at work to discover that his client had been assassinated. The assassin is already apprehended by the time he arrives, but something doesn’t quite seem right.

Fukuzawa gives Rampo a pair of glasses, claiming that wearing them would activate his ability to instantly determine the truth of any situation, and taking them off would give him the ability to tolerate the stupidity of the ordinary person.

The Detective Agency receives an urgent request from the government to investigate a series murders perpetrated by the same culprit.