The story follows the "strongest juvenile delinquent," Oga Tatsumi, who is a first year in "Ishiyama High," a school for delinquents. The story starts as he is telling the story of how he found the baby to his best friend Furuichi Takayuki. One day while doing laundry by the river (actually, taking revenge on people trying to kill him in his sleep), he sees a man floating down it. He pulls him to shore and it splits in half which reveals a baby boy inside. This boy is the son of the great demon king and he has been chosen as the one to raise it with the baby's maid Hilda. The story follows his life with the child and at the delinquent school.