The kappa, in Japanese folklore, are water goblins that are closely associated with a certain town in the country. Unfortunately, the area is also home to a militant splinter group of researchers dedicated to developing amphibious super soldiers based on the kappa of legends. When their experiments result in murders by some escapees, the appearance of an actual kappa, and the triggering of an atomic bomb, the consequences are of epic proportions. A monster arrives in the midst of the nuclear fallout, and Japan’s defenses are helpless against it. Mankind’s only savior is an irradiated water goblin that is on the rampage with death in its eyes.