Airi Sena, daughter of Yuihime Girls' Academy Principal Ranka Sena, attends as a second-year student, consistently achieving the highest academic grades in her year. Initially a vocal opponent of Yuihime's merger with Kagamidai Academy and the admission of male students, her stance shifts over several weeks until she accepts the merger and builds cooperative relationships with the transferred students.

Born and raised in Kagamidai's affluent Old District, Airi moves to a low-cost apartment in the New District upon enrolling at Yuihime. She lives independently, maintaining a frugal lifestyle that includes shopping for groceries and necessities at the local Kume Mart supermarket.

Elected class representative alongside male Kagamidai transfer student Shingo Uryū, their collaboration begins reluctantly but develops into mutual respect and effective coordination. Over time, Airi addresses Shingo without formal honorifics, reflecting growing familiarity. Their interactions extend beyond school; she invites him to her apartment during a rainstorm, and they share a bath with the lights off due to her embarrassment. Manga adaptations depict their relationship developing romantically, with Airi becoming Shingo's girlfriend.

Airi joins the Nuko Club, a group caring for injured animals, to help secure its official recognition. This requires her to arrive early for animal care duties, marking a change from her initial reluctance toward group activities. Her childhood friendship with Sana Inui remains important, gaining more prominence in later adaptations.

In the anime adaptation, which primarily follows Miu Amaha's route, Airi's character receives focus early on, depicting her resistance to the merger and subsequent warming to Shingo, while later episodes shift focus to other characters' storylines.