I can't wait till this awesome series premieres as an anime next year. Just like Ao no Exorcist, it is quite an alternative take on the 'son of the Devil' theme that we are used to see in classic movies like The Exorcist or The Prophecy.
We are used to think that the son of a demon is supposed to be the cusp of everything that is evil, but what if it really isn't so? That's the challenge that these stories present, with imperfect, human characters, yet with a sense of what is right.
Beelzebub is the story of Oga Tatsumi, a high-school freshman punk, pretty much like Kurosaki Ichigo from Bleach, who constantly fights and gets in trouble with gangs and social clichés in his high school, considered one of the worst in Japan, Ishiyama High.
Ishiyama High is more like the scenery of power struggles between gangs and its leaders, and we never see a teacher there, meaning that its students are all on their own in their perfect anarchy experiment.
One day Oga was kicking the living crap out of a group that defied him, and took them to the river to 'do the laundry', drowning them repeatedly in order to wash their blood stained clothes. (Erm, bear in mind that this is a dark comedy)
Until he sees a corpse emerging out of the river. Everyone is scared the hell out and runs, except Oga. The corpse splits in half like a capsule and reveals a really cute naked baby, who 'falls in love' with Oga's cruelty and dark aura.
He doesn't know what's going on and accepts to take care of the baby, who will be attached to his back until he finds someone darker and more cruel than him.
The baby is the son of the Devil in Earth, and to meet his true destiny, he must be raised in the worst enviroment possible in order to ensure the destruction of humanity. That's why Hilda, a Gothic-lolita caregiver and warrior from Hell, meets Oga to ensure that objective.
Thus the trouble and fun ensues :-)