The world that was once afflicted by Hadlar, the Dark Lord, has regained peace in the hands of a swordsman called the "hero" and his companions. Delmurin Island became a place where monsters released from the Dark Lord lived. Dai, who is the only human on the island and longs to be a hero, lives in peace with the monsters. However, that life completely changes with the resurrection of the Dark Lord Hadlar. With promises from teachers, encounters with friends, and a destiny that cannot be escaped... In order to save the world, the adventure of Dai and his quest to be a hero begins!