In 1200 A.D, Humans have made peace with Kaiju, especially Japan, well, at least most of the humans that are completely aware of the existence of Kaiju. It is the Gusuku Period in Japan, and the Kingdom of Infant Island and the Okinawan Locals are also at peace, protected by the ancient Kaiju guardian, Mothra. She comes into action when her enraged "brother," Battra, awakens and threatens the Earth.