A seemingly normal teenager and high school student, Gainer Sanga is a champion video game player with a penchant for combat games. Following his 200th straight victory, Gainer is awarded the title of "King Gainer" for his unrivaled skill in virtual battle. However, his carefree world of video gaming comes to an end when he is arrested in the middle of class by Adette Kistler on suspicion of being involved with the Exodus movement. Escaping confinement with a notorious Exodus contractor named Gain Bijou, Gainer's skill in combat is about to jump from the virtual world to the real thing, when the video game prodigy is tasked with piloting an Overman—a fierce fighting robot with a host of special abilities far superior to the standard Silhouette Engines which make up the mainstay of today's military forces.