Aria is a pale-skinned teenage girl who is acknowledged as being incredibly beautiful and attractive by virtually everyone with back-length light brown hair that has bangs hanging over the right side of her face with a single medium-length hair strand on the left side, light brown eyes and she is easily the most buxom character in the series.
She often has a calm and gentle look on her face that makes her seem motherly. Even Takatoshi Tsuda, who is generally immune to the charms of the various girls who surround him, is unable to resist her charms.
Despite being the daughter of the wealthy Zaibatsu Shichijō, Aria is far from a spoiled girl. In fact, she is extremely generous and more than happy to use her wealth for the sake of her friends. There are several occasions where she's brought the Student Council members to various places at her expense, and a few where she's brought along even more people.
One of Aria's most notable quirks is her airheadedness. This works in tandem with a "common sense" different from most people, most likely due to her upbringing, to create a surreal perception of the world and the goings-on around her. While she is level-headed on many occasions and is one of the most reliable people in the school given her position as the Student Council Secretary, she has also displayed misperceptions, presumptions, and made mistakes or have done things bordering on the nonsensical i.e. forgetting schools don't have escalators or sliding doors, not wearing underwear most of the time, wearing a chastity belt etc.
Of the Student Council members (barring Takatoshi Tsuda himself), Aria is the most mature. She has a warm and motherly feeling to her who is also calm to the point that Shino Amakusa and Suzu Hagimura often overreact.
That said, she is also the most perverted and twisted member of the Student Council, surpassing even Shino due to the fact Aria's sexual interests tend to be more extreme. She has expressed interest in things like enemas (for sexual purposes), exhibitionism and bondage (both as a submissive and as the dominant). This is arguably due in part to her parents and upbringing, as she has been privy to material and events that may have influenced her during childhood.
(Source: Seitokai Yakuindomo Wiki)
