Beelzebub Manga

This is the story of up-and-coming young delinquent Tatsumi Oga, a first year at the infamous Ishiyama High, who one day suddenly finds himself the unintentional adoptive parent to the Demon Kings's son himself, Kaiser de Emperana Beelzebub IV (Baby Beel for short), an adorable little baby boy who is destined to destroy the world. Initially reluctant to carry out his fatherly duties, Oga changes his mind when the demon nanny and "mommy" Hildegarde appears, informing him that, due to the contract made between them, he will die if he and Baby Beel are separated by 15 meters or more, and that he must face his responsibilities. Unless he can find someone even stronger to take over for him, that is...