The opening twenty minutes obliterate the entire Mazinger Army. Koji watches his friends die before he even reaches the cockpit, and the show never blinks. That weight carries you into a final fight that lasts five minutes but feels like the only thing that matters because everything before it cost so much to reach it.

The Mycenae Empire strikes from underground without warning, led by the Great General of Darkness in a campaign to conquer Earth. Seven generals serve under him, each commanding an army of Warrior Beasts that outclass their opponents, and the Mazinger Army falls before them. At the same time, Archduke Gorgon relentlessly pursues Koji Kabuto, determined to kill him before he can reach Mazinkaiser. Then a red light appears in the sky above Mount Fuji, a sign that the greatest battle in history is approaching. The result is a single-episode mecha action OVA built around giant robots and a war for the planet's fate.