Ishiyama High, a school teeming with troublemakers, sets the stage for chaos and brawls. Amidst this unruly environment, first-year student Tatsumi Oga reigns as the fiercest combatant. One fateful day, Oga's life takes a bizarre turn as he stumbles upon a man drifting along a river, who unexpectedly splits open to reveal a baby known as Kaiser de Emperana Beelzebub IV, affectionately called Baby Beel. Unbeknownst to Oga, this infant is the son of the Demon Lord. Alongside Beel's demon maid, Hildegard, Oga embraces the daunting task of nurturing Baby Beel. Surrounded by delinquents and supernatural forces, they face challenges beyond their wildest imaginations.