The first episode begins in medias res, depicting the climatic final battle between the Photon Power Lab and Dr. Hell's forces. Meeting the attack head on are the Mazinger Corps and the Kurogane house, who attempt to stand their ground against Dr. Hell's three armies, led by Baron Ashura, Count Brocken and Viscount Pygman. As the battle is being waged we find out that the protagonist Kouji has been missing, and is shown to be in an unknown location, for unknown reasons. While there he meets a variety of strange beings including Zeus. By the time he returns, Dr. Hell's forces have already defeated most of his comrades and Kouji prepares to defeat Dr. Hell, for their sake.
The beginning shows a wrecked Mazinger Z slumbering away from the Dark General. This will be the continuation of Episode 26, where the Dark General comes and Mazinger Z uses the Big Bang Punch to ram the Dark General. The story moves back to the very start of the events which lead to the previous episode. Kouji and his brother, Shiro, are living with their grandfather, Juzo, while mysterious murders occur around their manor. Investigating these murders is Inspector Ankokuji, who was also hired to be Juzo's bodyguard, while Dr. Hell and Baron Ashura prepare for their first attack on the Photon Power Lab. In the meantime, Boss and his gang kidnap Shiro in order to lure out Kouji and beat him. After Kouji fights Boss, Baron Ashura attacks his household with the gigantic robot known as "Talos", forcing Juzo to send out the Pilder to Kouji and Shiro. Moments later, Juzo activates the product of years of research: the Super Robot, Mazinger Z.