In a ruined world, a strange disease that turns humans into "Kaijin" suddenly begins to spread. Those who contract this "Monster Disease" have both their physical abilities and their primal desires amplified, turning into violent rioters who attack regular humans. A man named Yudex harbors an abnormal hatred for these terrifying infected individuals. Believing that the key to his lost memories lies within this hatred, he begins to eliminate the infected one after another. In response, "Xenos," an organization made up of those infected by the Monster Disease, begins to take action to take Yudex down. [BAD END]