A maritime expedition shipwrecks on Infant Island, which is believed to be uninhabited due to radiation from nuclear tests. However, survivors of the expedition report discovering a small, isolated tribe of natives who worship a colossal creature named Mothra. These peaceful islanders have retained their serenity and culture despite the harsh environment. When a joint Rolisican-Japanese expedition led by entrepreneur Clark Nelson lands on the island, they discover not only the natives but also two tiny female fairies, known as the Shobijin. Fascinated by their mystical singing abilities, Nelson kidnaps the Shobijin and takes them to Tokyo to exploit them commercially.

The Shobijin’s abduction prompts concern and generates significant media attention. Unbeknownst to Nelson and his team, their disruptive actions awaken the powerful entity the islanders revere: Mothra. The gigantic moth larva hatches from its egg and begins a destructive journey towards Japan to rescue the Shobijin. Mothra traverses the ocean, undeterred by various military efforts to halt its progress. As the creature draws closer to major cities, journalists, scientists, and government officials scramble to decipher the connection between Mothra and the ancient traditions of Infant Island, fearing the catastrophic potential of its wrath.