Dragon Quest is loosely based on Dragon Quest III. The names and some of the characters are familar, but the world map is smaller and a very different shape. The two main characters are Abel and Tialah. Tialah receives the legendary Red Stone from the Aliahan Village sage Master Yogi. Soon after, Tialah is kidnapped by the evil Baramos who wants to use the Red Stone to resurrect The Great Dragon and be granted eternal life. Abel swore to rescue Tialah and he is given the Blue Stone, which can only seal the Dragon once it has been released.

[Source: AniDB]

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.

[Source: MyAnimeList]

After the defeat of the demon lord Hadlar all of the monsters were unleashed from his evil will and moved to the island of Delmurin to live in peace. Dai is the only human living on the island. Having been raised by the kindly monster Brass, Dai's dream is to grow up to be a hero. He gets to become one when Hadlar is resurrected and the previous hero, Avan, comes to train Dai to help in the battle. But Hadlar, announcing that he now works for an even more powerful demon lord, comes to kill Avan. To save his students Avan uses a Self-Sacrifice spell to attack, but is unable to defeat Hadlar. When it seems that Dai and Avan's other student Pop are doomed a mark appears on Dai's forehead and he suddenly gains super powers and is able to fend off Hadlar. The two students then go off on a journey to avenge Avan and bring peace back to the world.

[Source: Anime News Network]

Dragon Quest Dai no Daibouken Movie 2

Dragon Quest Dai no Daibouken Movie 03.

The adventures of Arus's childhood.

Luca follows in his father's footsteps to rescue his mother from evil Ladja. Finding the heavenly hero who wields the Zenithian sword is his only hope.

[Source: Netflix]

At one time, the world was suffering under Hadlar, the Dark Lord. That is, until peace was won back by Hero swordsman and his companions…

Time has passed… Monsters liberated from under the demon king now live on Dermline Island, a solitary island in the south seas.

A boy named Dai is the only human on the island. He wants to become a Hero, and he’s been living in peace with the monsters. But his life is transformed when Hadlar is resurrected.

A promise to a mentor; encounters with companions; an unescapable destiny… Young Dai begins his adventure to become a Hero, and to save a world once again in crisis!

[Source: Toei Animation Europe]