Ten years after the end of the war against Dr. Hell and his Mechanical Beasts, the world lives in an era of peace thanks to the development of photonic energy for peaceful purposes. Mazinger Z's pilot Koji Kabuto has become a distinguished scientist, after his father and grandfather, while Sayaka Yumi is now the director of the Photon Research Institute, after her father, Dr. Yumi, became the Prime Minister of Japan. Great Mazinger's pilot Tetsuya Tsurugi is still in the military and married to Jun Hono, who's expecting their first child. Koji's younger brother Shiro is also a military mecha pilot.