The story follows the "strongest juvenile delinquent", Oga Tatsumi, a first year in "Ishiyama High" the school for delinquents. One day while sleeping next to a river he sees a man floating down it, he pulls him to shore and the man splits in half revealing a baby boy. This boy is the son of the demon king and he has been chosen as the one to raise it with the baby's demon maid Hilda. The story follows his life with the child and at the delinquent school.