She is Kaname's older sister. In contrast to Kaname, Aya is a lazy ditz, but Kaname considers her on the "genius side" for her great learning capacity. In contrast with that, she usually misunderstands important things and she gets really confused in the blink of an eye. Her favourite hobby is probably playing video games and she usually nags Kaname into playing with her. She had a crush on Nasa.   
Tsukasa considers her a pretty girl and according to Nasa, she was very popular in middle school.