The gods banish a unicorn for the crime of making people happy, and the West Wind refuses to let it happen. That opening thirty minutes builds a world where kindness itself is dangerous, where one creature's gift threatens divine order. The rest of the film never quite recovers that weight, but those early scenes prove Osamu Tezuka understood something most children's stories miss: innocence doesn't protect you from jealousy.

A unicorn named Unico has the power to make anyone he meets happy, though no one knows whether it comes from his personality or from his horn. The gods grow jealous, believing only they should decide who is happy, so they banish Unico to the Hill of Oblivion and order the West Wind to carry him there. Unable to bear dooming someone so innocent, she instead takes him from place to place and from one era to another, on an endless flight from the gods' anger. Along the way Unico meets Beezel, a devil child, and Katy, also called Chao, a cat who longs to become a witch. Whether he can win their friendship is the heart of this fantasy adventure film.