This sequel to FRANKENSTEIN CONQUERS THE WORLD (although the Frankenstein element is dropped from the English version) begins with a gargantuan creature attacking ships and eating human beings. The authorities quickly believe that this creature was the same one that escaped from the research laboratory headed by Dr. Paul Stewart. His colleagues, Akemi and Majida, disagree with the authorities. The scientists declared that the gargantua they had was gentle. The Self Defense Force wastes no time in tracking down the horrendous beast and almost succeed in killing it... until ANOTHER GARGANTUA comes to its aid. Now the world is faced with two Gargantuas!!! Is there a way to stop these giant Frankenstein monsters?