An explosion that occurred five years ago leads to the spread of Nanobots into the atmosphere, infecting every living being. These nanobots become active within the infected beings, mutating them and creating creatures known as E.V.O., which are half-robot, half-human androids. Rex is one of these EVOs. However, it is not the Nanobots that control Rex, but Rex that controls the Nanobots. Some EVOs misuse these abilities. Rex is a normal 15-year-old human, but after the explosion, he loses his memory and transforms into an EVO. However, instead of being controlled by EVOs, he controls them. While the EVOs grant him many powers, they also give him the ability to heal other EVOs.
