20XX. A series of brutal incidents perpetrated by the mysterious organization [Adonis] occurs one after another in the streets of Shinjuku. —Commonly known as the [X-Day Incidents]. In Shinjuku, now transformed into a dangerous city, police officer [Hoshino Ichika] had been working tirelessly every day to ensure the safety of the area. One night, she is attacked by an unknown assailant and fitted with a collar containing a hidden poison. In her confusion, Hoshino decides to investigate alongside a group of men who are independently pursuing the [X-Day Incidents]—former members of the police organization. Amidst this, a new incident involving a leaked handgun from Shinjuku Ward emerges, and an inspector is dispatched from the Metropolitan Police Department to take charge of the investigation. His name is [Shuuwa Mitsuru]. As various emotions and motives intertwine, Hoshino and the others must confront the unfolding incidents—