The manga starts off as just an average day until the sudden appearance of a gigantic masked woman wearing no clothes on her torso. The people of Tokyo are frightened, while others just stare perversely. Koji Kabuto and Mazinger Z are sent out to fight the masked woman, thinking she might have been sent by Dr. Hell. The woman, Kekko Kamen fights back by distracting Koji with her nude body and acrobatic fighting style, managing to restrain the Mazinger.
Meanwhile Dr. Hell and Baron Ashura uses this as an opportunity to strike the Photon Power Laboratory. Sayaka Yumi however stands in their way, having stripped down to only her gloves and boots to distract the Iron Masks after watching how Kekko Kamen managed to overpower Z. Blown back, Dr. Hell summons Mechanical Beasts to attack the Photon Lab.
Back at the city, Koji learns that Kekko Kamen is not an enemy, and does not even know how she got so big. Prof. Yumi contacts Koji, informing him that the lab is under attack sending out the Jet Scrander. Kekko Kamen decides to help out by hijacking the Scrander and flying towards the lab, with the Mazinger running after her. At the lab, Kekko Kamen destroys some of the Mechanical Beasts but the Jet Scrander is destroyed, before she can be finished off the Mazinger uses its Breast Fire to destroy the last Mechanical Beast while burning off Hell and Ashura's clothes, forcing them to retreat. The Mazinger Z holds Kekko Kamen in its arms after the battle to help her back up.