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.
Fyodor Dostoevsky makes his move on the Armed Detective Agency and the Port Mafia as he plants the Cannibalism poison into both of the group's leaders.
The Detective Agency president is in safe hands for now, but unless he or the Port Mafia boss dies, a full-scale war between the two organizations is inevitable.