Dai has grown up the only human on an island of monsters, raised peacefully by the kind monster Brass and dreaming of becoming a hero despite having no one to be a hero against. That changes when impostors try to steal the island's Golden Metal Slime and Princess Leona arrives asking for help, pulling Dai toward a wider world of danger under the guidance of the veteran hero Avan. This manga is the original story behind the Dragon Quest: The Adventure of Dai franchise, whose 1990s television dubs introduced its hero to Latin American and Brazilian audiences under the name Fly.