Dragon Quest: Dai no Daibouken (1991)
Dragon Quest Dai no Daiboken
Dragon Quest: Great Adventure of Dai
ドラゴンクエスト ダイの大冒険
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.