Aya Misaki

Aya is one of Mariko and Nanako's class mates. The daughter of a famous lawyer, she wishes with all her strength to become a member of the Sorority, like her mother had been when she was young. The main target of her wickedness and malicious remarks is Nanako, as Aya thinks she's completely unworthy of being a Sorority member. Some time later, Mariko, who's always been in competition with her, will become her main target. She has two friends supporting and following her almost everywhere, Furuta and Sonobe.

She's better described in the anime version, where we get to know some elements of her past and some hidden aspects (like her sweetness and solitude) of her personality and behaviour. (from http://members.tripod.com/~aoisora)