At Ishiyama High School, Tatsumi Oga commands both fear and rivalry among the delinquents. However, his focus shifts dramatically when he becomes the caregiver of Baby Beel, the son of the Demon Lord. Tasked with raising the powerful infant by Beel's maid, Hilda, Oga must either embrace his new role or find a substitute caretaker who surpasses his strength. To lighten his burden, Oga considers enlisting one of the Tohoshinki, the school's elite fighters, to care for Baby Beel and relieve him of his unexpected parental duties.