Tatsumi Oga is called the “strongest juvenile delinquent” and he attends the first year in Ishiyama High School, a school for delinquents. One day he was sleeping next to a river, when he saw a man floating down it. Oga pulled him to shore and then the man split in half, revealing a baby boy inside. This boy is Beelzebub, the son of the demon king, and Oga has been chosen as the one to raise him. The story follows the Oga’s life at the Ishiyama School while he tries to raise Beelzebub.