Long ago, the world suffered from wicked demons controlled by the cruel dragon, Diabolos. Yet, a brave hero named Zard emerged at only seven years old and defeated Diabolos, calming the demons and bringing peace to the land. Unfortunately, Diabolos returned four years later, causing the demons to attack once more. Zard set off to face Diabolos again but never returned. Now, in the year 4996, Zard's dear friend Kai embarked on a journey to see if Zard's dream of humans and demons living together could come true. Along the way, he met Izayoi, a mystical youth who could communicate with demons using his heart, and Gend, an agile swordsman from the dwindling Dark Elves tribe. Knowing they held the key to uniting humans and demons, Kai decided to join them on their quest.