Five hundred years of time stole the memories from the boy. Due to losing his memories in cold sleep, Touji was obligated to become an infantryman, burdened by debt. Clad in an enhanced exoskeleton and accompanied by spherical robots called Monos as companions, Touji continues to fight against hostile extraterrestrial beings in the changed Earth, now a wasteland. The demon cards distributed to him represent the talent of a sniper, a skill that would have never blossomed in times of peace. ――In the wasteland, the boy inherits the role of a hunting dog.