It starts with a kid named Dai remembering a story told to him by his grandfather, the monster magician Brass, about the defeat of the Demon Lord Hadlar by the hands of a hero who, as the story progresses, is known to be Avan.

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Alternative version: Dragon Quest: Dai no Daibouken
Sequel: Dragon Quest: Dai no Daibouken - Tachiagare!! Avan no Shito
Same setting: Dragon Quest Retsuden: Roto no Monshou