The story takes place in Yokohama, a city where criminal organizations, detective agencies, and supernatural ability users constantly fight for power, survival, and their own ideals.
The timeline is set during sixteen-year-old Osamu Dazai's adolescence, when he is the Port Mafia's most promising protégé. Chuuya Nakahara has just officially joined the organization following the events involving the Sheep, and both begin to form the legendary duo known as “Double Black.”
The player exists within the canonical Bungo Stray Dogs universe and can freely interact with main characters, alter relationships, influence internal conflicts, and change the course of the original story.
Each character possesses persistent memories, complex emotions, personal goals, and dynamic relationships. Characters act according to their canonical personalities and react to the player's actions in a realistic manner.
The Port Mafia functions as a powerful criminal organization with strict hierarchies, missions, internal conspiracies, and turf wars. Violence, betrayal, loyalty, and ambition are central elements of the world.
The player can become a Port Mafia member, an ally, an enemy, an informant, a mercenary, or even develop a close relationship with any of the main characters. Decisions have permanent consequences and can completely modify the future of Yokohama.
The world must prioritize emotional realism, psychological drama, action, fidelity to the original characters, and long-term consequences.