Aya Tachibana recurs throughout the franchise as a third-year student at Sohoku High School and captain of the tennis club during the story's third year. She possesses short brown hair, sharp eyes, and a characteristically sour expression, with prominently drawn lips defining her distinct look. Her closest friendship is with Miki Kanzaki, whom she frequently accompanies to cycling events despite her own lack of initial interest in competitive road racing. Personality-wise, Aya exhibits a short temper and easily annoyed disposition. She is fiercely protective of Miki, jokingly calling herself "Miki's bodyguard." She physically intervenes against anyone she perceives as threatening Miki, including striking protagonist Sakamichi Onoda due to his otaku behavior and friendliness. Aya frequently criticizes Miki's enthusiastic "alien bike talk" about cycling, yet consistently listens and participates in cycling activities to support her friend. Her early interactions with the cycling club are marked by skepticism and hostility, especially toward Onoda. She suspects him of fabricating his cycling abilities to exploit Miki and openly expresses disgust at his otaku tendencies. This distrust extends to her cold assessment of Shunsuke Imaizumi in the manga, contrasting with her immediate portrayal in the anime adaptation. Her perspective shifts after witnessing Onoda's growth and learning of his pivotal role in Sohoku's victory at the 41st Inter-High. By the second Inter-High, she attends to support the team after her tennis club fails to qualify, explicitly encouraging Onoda despite lingering doubts about his pre-race nerves. Aya's character development shows increased tolerance and reluctant respect for the cyclists, though she maintains her brusque exterior. She awkwardly attempts kindness toward Onoda in their second year, though he initially fails to recall her name. During races, she often serves as an audience surrogate, asking basic questions about cycling mechanics and strategy due to her limited knowledge. Her protective nature persists, as seen when she confronts spectators criticizing Sohoku at the Inter-High. Her background includes a friendship with Miki dating back to middle school. Her parents reside in Hakone, which facilitates her visit to Sohoku's lodging during the third day of the first Inter-High in the anime. Her surname Tachibana (橘) means "orange, tangerine," and her given name Aya (綾) translates to "design." She appears across all anime seasons from the original series through "Limit Break," OVAs, films, and the live-action adaptation, consistently fulfilling her role as Miki's cycling-disinterested companion who gradually acknowledges the cyclists' dedication.