Keisuke Jin was the son of Robotics scientist Keitarō 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.