Kouji and his friends have defeated Dr. Hell and are now enjoying a break, but suddenly a strange prophet appears and warns everyone of an oncoming danger, mechanical beasts never seen before start appearing all around the world wrecking havoc. Its up to Kouji and his Mazinger Z to stand up to this threat but it seems he is vastly outnumber and outmatched.

This film served as an alternative link between the Mazinger Z TV series and the Great Mazinger TV series. It basically introduces Great Mazinger to the audience, as well as his enemies from the Mikene Empire.