Keisuke Jin was the son of Robotics scientist Keitar� Jin who was devising the technology for undersea exploration. However, Keisuke and his father were attacked by Neptune of the G.O.D. organization which wanted the technology for their use. As a result, Keisuke suffered mortal injuries inflicted from the ordeal with his father forced to perform surgery on his son with what little of his inventions to make his son into a "Kaizorg" to save his life before he succumbed to his own injuries. Driven to avenge his father's death and save the world, Keisuke battles G.O.D.