Gunjo Gakuenis a facility designed to gather students with a high adaptation coefficient (indicating that the student is less likely to be able to adapt to society), determined from an adaptation exam mandated by the government. After a failed summer vacation with other members of the school's broadcasting club, Taichi Kurosu and some of the other club members return to the city to find that all living creatures within it except for the club members have completely vanished. (wikipedia.org)