Dr. Hell develops a gun that can increase an object's size to giant proportions. Baron Ashura uses it on a local student's robotic science project in order to create a giant killer robot to rival the power of Mazinger Z.
The school's winter festival is interrupted by the attack of Baron Ashura's latest mechanical beast. While Aphrodite S does battle against the creature, Koji must fend off Ashura's armored troops as they invade the Kabuto residence.
Doctor Hell unleashes the Deviler X1, a mechanical beast capable of aerial assaults. Since Mazinger Z does not possess flying capabilities, Koji must come up with a plan to defeat the Deviler X1 from the ground.