Damnant Quod Non Intellegunt

(This is Killugon)
Damnant quod non intellegunt: "They condemn what they do not understand."
So, rich kid who everyone hates and is pushed by his family to be that stuck up asshole he's expected to be. That's basically how you'd sum up Killua Zoldyck in one, lengthy, sentence. But it wouldn't be an interesting story if that's all it was about.
In Killua's attic, where he goes to get away from his oppressive parents, he finds a book filled with runes and Latin and decides to just try one of the pages -- not like it would cause him any harm.
Here he ends up summoning a demon, and not just any demon, one of the head demons in hell, and, as you'd expect, the summoned is less than happy with this rich brat.