"Beelzebub: Hirotta Akachan wa Daimaō!?" centers on Tatsumi Oga, a delinquent high school student at Ishiyama High, a school notorious for its violent and unruly environment. One day, while by a river, Oga encounters a man floating downstream. Upon rescuing him, the man splits open to reveal a baby named Kaiser de Emperana Beelzebub IV, the son of the Demon Lord. Oga is chosen as the caretaker for Beelzebub, tasked with raising him to become the future ruler of the demon world. This responsibility comes with the constant presence of Hildegard, Beelzebub’s stoic and powerful maid, who ensures the baby’s safety and Oga’s compliance.

As Oga navigates his new role, he is thrust into a series of chaotic and comedic situations. Beelzebub possesses immense destructive power, often unleashing it unintentionally, which complicates Oga’s life further. Despite his tough exterior, Oga gradually forms a bond with the baby, though he frequently struggles with the absurdity of his predicament. The series explores Oga’s interactions with other characters, including his best friend Furuichi, who becomes entangled in the supernatural events, and Hilda, whose no-nonsense demeanor contrasts with Oga’s brash personality.

The narrative expands as Oga faces various adversaries, both human and demonic, who challenge his strength and resolve. These encounters often involve battles that showcase Oga’s growing abilities, as well as the unique powers of those around him. The series balances action with humor, often deriving comedy from the juxtaposition of Oga’s delinquent lifestyle with the absurdity of raising a demon baby. Themes of responsibility, loyalty, and unexpected familial bonds are woven throughout the story, as Oga’s journey shifts from reluctant caretaker to a determined protector of Beelzebub. The dynamic between the characters, combined with the blend of supernatural elements and everyday high school life, creates a distinctive and engaging narrative.