Oga Tatsumi, the toughest young offender, is the protagonist of the tale. He's a freshman at Ishiyama High, a delinquent school. One day, while dozing by a river, he spots a man drifting in the water. Oga drags the man to the shore and the man parts into two, revealing an infant son of the devil. He is summoned to raise the boy together with Hilda, the maid-devil. The narrative centers around Oga's life with the youngster and his dealings with the delinquent school.