One night, high school second-year Nishina Airi is abducted on her way home from a part-time job. She wakes up in an unfamiliar sealed room along with nine other students from her school, all of them wearing metal collars around their necks. A voice from a speaker announces that they will be forced to play a real-life werewolf game with no right to refuse. Two of them are werewolves who kill one villager each night, and the villagers must vote each evening to execute one person they suspect of being a werewolf. Defying the rules results in instant death through the collars. Airi's friend Naoko tries to leave and is killed on the spot, making it clear that the game is deadly serious.

The participants are assigned roles: villagers, werewolves, and a single prophet who can investigate one person's true identity each night. Airi is a villager. As the game progresses, players are executed by vote during the day and killed by werewolves at night. Tensions rise as it becomes clear that the participants have hidden connections and grudges against one another, revealed through video messages displayed in their rooms. Airi forms a cautious alliance with a calm classmate named Tomohiro Tada, who seems to be looking out for her.

Through a series of votes and deaths, the group narrows down the suspects. The prophet Marie Inoue identifies one player, Seiichiro Machimura, as a werewolf, but another player, Takeshi Fujiki, claims to be the real prophet and calls her a liar. After a complex chain of accusations, Marie is executed, and Fujiki is killed the next night. This leaves only Airi, Tada, and Konomi Inoue alive. Airi realizes that either Tada or Konomi must be the remaining werewolf. Despite trusting Tada, she votes for him, and he is executed. The villagers win the first round.

As Airi loses consciousness from the collar, the speaker announces the end of the first half. She wakes up in a new room with a new group of students and a new game about to begin. Her role card this time reads werewolf. Konomi is also there, also a werewolf. The voice says that werewolves are specialists of the game. Airi, now hardened by her experience, begins coldly planning who to kill next. The story continues in the sequel, Beast Side, where Airi must survive as a werewolf while struggling with her humanity.

The manga adaptation covers the first two arcs of the novel series: the original game from the villager's perspective and Beast Side from the werewolf's perspective. The setting is a sealed facility with individual rooms, a common area, and a monitoring system run by an unknown organizer who broadcasts the game. The core conflict is survival through deception and deduction under the constant threat of death. The narrative explores how extreme circumstances push ordinary people to betray, kill, or break down, and how survival changes a person's nature.