The story begins with a young boy named Dai remembering a story told to him by his adoptive grandfather, the monster magician Brass, about the defeat of the Demon King Hadlar by the hands of a hero known as Avan. After the defeat of the Demon King Hadlar, all of the monsters were released from his evil will and peace reigned supreme around the world once again for ten years. Some monsters and demons moved to the island of Delmurin to live in peace. Dai, the young protagonist of the series, is the only human living on the island. Having been raised by Brass and with his best friend, the monster Gome, Dai grows up dreaming of becoming a hero.
Dai can do nothing but watch. Finally, the showdown between Avan and Hadlar is concluded.
Avan turns into a dragon and attacks Dai. Dai fights back to no avail. To defeat Avan’s flames requires Wave Slash.
A dark power affects Dai’s monster friends, driving them berserk. Brass tries to get Dai to leave.
Avan is overpowered by Hadlar, who is now stronger than ever. To protect his students and the world, Avan gathers the last of his strength and faces Hadlar.
After the harrowing events that transpired, Dai says his goodbyes to all his monster friends on Delmurin Island and begins is great adventure with Brass.