Kiryu is undergoing repair modifications after its battle with Godzilla. Prime Minister Hayato Igarashi The Shobijin (Mothra's twin fairies) warn the Japanese government that Godzilla continues returning to Japan because they used the original Godzilla's bones in Kiryu's design. If they return the bones to the bottom of the sea Mothra would gladly take Kiryu's place in defending Japan, but if they do not, Mothra will declare war on humanity. In the end will the survivor be monster, robot or mankind?