Kasumi and her sister, Shizuku, were infected with the Medusa virus, which slowly eats away at the body. There is no cure, but of the two only Kasumi is selected to go into a cryogenically frozen state along with 159 others until a cure is found. In the undetermined future, Kasumi awakens to find herself and others, who were in suspended animation in an unfamiliar world with bloodthirsty monsters. Kasumi struggles to survive in a treacherous world in order to unlock its mysteries and learn the fate of her twin sister