Beelzebub

Beelzebub Oga, a first-year student at Ishiyama High, is a notorious delinquent and the most feared student in school. One day, while by the river, he encounters a mysterious man who splits in half, revealing a baby who attaches itself to Oga's back. The baby is revealed to be Kaiser de Emperana Beelzebub IV, the son of the Demon Lord, and is soon joined by his demon maid, Hildegard, who insists that Oga take on the responsibility of raising the young demon as his guardian. Surrounded by the school's juvenile delinquents and demonic powers, Oga and Beel embark on a challenging journey to raise the future Lord of the Underworld.