Aya is the one who initially describes Miki as a "bike otaku" and tends to criticize her for "having her head in the clouds" or getting distracted from important or obvious things due to her love of cycling. Though Aya doesn't have much interest in cycling and finds Miki's excitement over bicycles confusing, she still listens to Miki when she talks about her interest. Miki also tends to lightly tease Aya for being prickly or awkward when trying to be nice to Onoda, much to Aya's displeasure.
Despite all of this, the two get along quite well, and Aya is a good friend of Miki's. Aya cares for Miki to the point of being somewhat overprotective of her, and is quick to strike any otaku that tries to converse with her, as well as anyone who makes perverted or strange comments towards her, as seen when she hits Onoda for acting (in her eyes) untoward towards her. She calls Miki "helplessly cute" for not suspecting Onoda of lying about his cycling ability in order to impress her.
In second year, Aya tags along with Miki and the rest of the support crew to the Interhigh when her own team loses their qualifiers, often turning to Miki when she becomes confused about the state of the competition. Though she often vocalizes her displeasure about all the work they have to do, she seems to be becoming more and more interested in cycling.
Miki calls her "Aya-chan."
Aya initially finds Onoda disgusting. She is quickly put off when he reveals himself as an otaku (going so far as to hit him when he starts acting too friendly towards Miki for her comfort) and immediately suspects of him of lying about his seemingly impossible bike rides to Akihabara in order to take advantage of Miki's obvious love of cycling. However, after seeing his growth and hearing from Miki about his victory at the first Inter High, she seems to develop a bit of respect for him. In the manga (or the movie), she struggles at first, but congratulates him for his victory.
Aya tags along with Miki for Onoda's second Inter High, much to Onoda's shock. She tells him to do his best, surprising him even more. Aya seems to have become more friendly with Onoda, although she has doubts as to his supposed status as the team's ace after seeing his nervous pre-race fumbling (to the point of asking Miki if she should hit him to clear his head).
Though Sugimoto doesn't seem to be friends with Aya, she occasionally notes his loud and showy mannerisms. In the anime (where Aya joins the support team on the third day off 41st Inter High) she points out his lack of faith in his own team (and subsequent hypocrisy when he turns around when things look to be in their favor once more).