Under the guise of a "study trip", a group of students from , a junior high school operated by the fictional Kagawa Prefecture town of Shiroiwa, are corralled onto a bus and gassed, only to awaken in a school on an isolated, vacated island, wearing metal collars around their necks.
In the end, only four students remain: Shuya Nanahara, Noriko Nakagawa, Shogo Kawada, and antagonist Kazuo Kiriyama.