Shipwreck survivors are found on Infant Island, which was presumed uninhabited due to Rolisican atomic tests. Investigating the case is reporter Zenichiro "Snapping Turtle" Fukuda and his photographer Michi. The castaways attribute their survival to a special juice created by the natives of the island which leads to a joint expedition of Rolisican and Japanese scientists. Fukuda stows away on the expedition, which is headed by linguist Shinichi Chujo and Clark Nelson, an exploitative Rolisican businessman. The group encounters two tiny twin girls that Fukuda dubs the Shobijin, who worship the island's mythical deity named Mothra. After Nelson kidnaps the tiny fairies and beings to exploit them for profit, Mothra sets out on a journey to rescue them.