Mai Asahina is a student at Hakujō Academy, attending the same class as the protagonist Yūto Ayase. She is known for her quiet and reserved personality, which provides a calm contrast to the more energetic and boisterous nature of her close friend, Ryōko Sawamura. Her demeanor is often described with terms like graceful, kind, and tranquil, possessing a composure reminiscent of a miko or shrine maiden. This elegant and gentle bearing contributes to her popularity among the male students, even leading to her nomination for a school beauty pageant. Physically, she is recognized by her brown hair, which is about chest-length and styled with twintails and blunt bangs, and her purple eyes; she also often wears glasses, hair ribbons, and a necklace.

Within the school, Mai holds the position of vice-chairman of the naginatajutsu club, demonstrating a notable level of skill and dedication to this traditional Japanese martial art. Her closest friendships are with Ryōko Sawamura and Shiina Amamiya, another skilled practitioner of naginatajutsu and piano. The three girls are frequently seen together as a trio, with Mai and Ryōko often acting as supportive friends to Shiina. Mai's role in the story expands significantly from the first season, where she appears in brief cameos, to the second season, Haruka Nogizaka's Secret: Purezza, where she becomes a regular supporting character. In this larger role, she, along with Ryōko, discovers Shiina's romantic feelings for Yūto and actively encourages her in those pursuits, thereby influencing the evolving relationship dynamics among the main cast. Her established traits and her function as a supportive friend within the main social circle remain consistent throughout the series and its related media. Her primary ability lies in her proficiency with the naginata, a skill that reflects her disciplined and composed character.