The battle to determine who will be the next king of the demon world takes place every 1,000 years in the human world. 100 demons each own a spell book that allows them to draw out their unique powers, and they must team up with a human in order to fight for their own survival. Gash Bell, a happy-go-lucky but fiercely determined child, is one of 100 demons chosen to fight in this battle. His partner is Kiyomaro Takamine, an aloof junior high prodigy who could learn a thing or two from Gash and his optimistic approach to life. The bond between Gash and Kiyomaro deepens as they continue to survive through many harsh battles in Gash's pursuit to become a "kind king."