"There's no screw-up bigger than him! He's totally bad luck!" - Aya to Miyagi on Chihaya, Vol. 1 Chpt 3
Aya is one of the supporting characters of Earthian. She is an angel of Eden who chose to become a minus checker because of her hatred for the Earthian. Aya starts out as an antagonistic force to Chihaya and Kagetsuya's relationship.
There isn't much focus on Aya's background in the manga. However, it can be concluded that she comes from a well-off family as she is Kagetsuya's cousin, always dresses well and thinks highly of herself. Since she and Kagetsuya are related, she has known and loved him for a much longer time than Chihaya has. She also knew of Chihaya and his black wings way before he started attending her school. She pins him as bad luck immediately.
Aya has a relatively short, hourglass physique. Her long purple hair is mostly unstyled, save the two long braids on either side of her square bangs. Her eyes are blue and her wings are white.
In the words of Miyagi, Aya always has "something to bitch about". She is brash in every sense of the word and only seems truly happy when Kagetsuya is around. She openly flaunts her love for him and is vocal about her dislike of Chihaya and their partnership. While she would rather be Kagetsuya's partner, she refuses to become a plus checker because she hates the Earthian more than she loves him.
Like her cousin, Aya gets worked up quite easily. However, unlike Kagetsuya, she is rarely ever calm. She is rather emotional, sometimes reaching the point of tears in the midst of her frustration or rage. Despite all of this, she can be quite loving and caring when she's cares deeply enough about someone.
Throughout the series she constantly rejects Miyagi. At the end of the series she realizes that she will never be with Kagetsuya and marries Miyagi.
"I love Kagetsuya, but you're probably the only man who can make me happy." - Aya to Miyagi, Vol. Chpt.
"I knew you way before him! I'm the one who always loved you, Kagetsuya!" - Aya on Kagetsuya