Prince En Arc

The Prince En arc is the fourth story arc in the Beelzebub series. In the Manga, it's comprised of Chapters 77-113 while the Anime adaption follows Episodes 37-50. This arc introduces Baby Be'el's older brother En and his three wet nurses, as well as Zenjūrō Saotome. This arc also details the introduction of Behemoth's 34 Pillar Division.

Synopsis
Spoiler warning: Plot and/or ending details follow.