Kasumi Ishiki is one of 160 people infected with the Medusa virus, a plague that turns the body to stone, picked by the Venus Gate Corporation for cold sleep until a cure is found. She goes under without her twin sister Shizuku, who was not selected. When Kasumi wakes, the sealed facility is overgrown with thorns and roamed by monsters, most of the other sleepers are already dead, and the handful of survivors have no answers about what happened while they slept.