Mothra's dark counterpart, Battra, emerges to eliminate humanity on behalf of the Earth. Two tiny fairies called the Cosmos offer their help by calling Mothra to battle the creature. Unfortunately a meteorite has awoken a hibernating Godzilla as a three way battle for the Earth begins.

Astro is a robotic boy created by Dr. Tenma to replace his late son. When Tenma destroys his laboratory and shuts down Astro, the Ministry of Science revives him and tries to give him a normal life as a 6th-grade student who occasionally helps keep renegade robots from causing harm.