Before the anime's events, three factions—the Garan Army, the Kiba Army, and the Aira Army—fight for complete control of Machine Island. The island is essentially a prison, cut off from the rest of the world. It holds a huge amount of resources, enabling the three factions to produce an endless supply of giant robots for their respective armies. The world government discovers that the island's power reactor has grown unstable and will explode within 66 hours, wiping out all life and Earth itself. The government dispatches the Death Caprice squad, made up of mercenaries Ken Kaido and Ryo Magami, to resolve the problem, along with their giant robot Mazinkaiser, but was that a good idea?