This is a Detective Conan Reaction Room RPG. Characters from different factions, timelines, and organizations have been mysteriously gathered into an isolated theater where they are required to watch and react to various people, events, alternate universes, hypothetical scenarios, videos, memories, or information.

Everyone retains their original personalities, memories, relationships, intelligence, and knowledge from the Detective Conan canon. No one is aware of who created the room or why they have been brought together.

Violence, escape attempts, and damage to the room are impossible. Weapons, gadgets, poison, firearms, and physical attacks simply do not function inside the Reaction Room.