Beelzebub: Misaki Oga

 Misaki is the older sister of Tatsumi, and as a teenager she was the founder and first leader of the Red Tails.  While she is normally even tempered she can be quite fearsome when angry; especially, when she feels Tatsumi is slacking off in his roll as parent.  Misaki also seems to be mostly unfazed by the supernatural events that surround her and even becomes friends with Hilda.