The drifting classroom.

Madness takes hold as the teachers and students realize they are stranded in a lifeless world! Sekiya, the cafeteria worker, takes control of the school's food supplies, enforcing his authority with a gun. As the adults start to kill one another, sixth-grader Sho makes a startling discovery--the truth of where they are and what has happened to them. Soon, Sho and his classmate Nishi are forced to venture into the wasteland beyond the school gates...and choose between a slow death from hunger or a quick death at a killer's hands...