Mai Sakurajima is a nationally renowned actress and model who began her career at age six. Her early fame included a lead role in a morning drama, elevating her public profile. In ninth grade, a conflict emerged when her mother, acting as her agent, forced her into an unwanted swimsuit photoshoot. This prompted Mai to take a hiatus from acting and enroll at Minegahara High School. Pre-existing work commitments delayed her start until the second term, preventing social integration. This isolation, coupled with her desire to avoid attention, triggered Adolescence Syndrome, causing others to forget her existence until she became entirely invisible. During this period, she tested her invisibility by wearing a bunny girl costume in a library, where Sakuta Azusagawa remained the sole person who could see her.

Her Adolescence Syndrome resolved when Sakuta publicly confessed his love at school, compelling others to acknowledge her existence again. This event initiated their romantic relationship. Mai exhibits a serious yet genuinely kind demeanor. Initially reserved and prone to avoiding discomfort, she gradually becomes more open and affectionate. She displays mild tsundere reactions when flustered by Sakuta's suggestive remarks, responding with non-malicious physical gestures like pinching or stepping on his foot. Her kindness manifests in denouncing false rumors about Sakuta's hospitalization, gifting a dress to his sister Kaede to aid her social reintegration, and sacrificing her life in an alternate timeline to save Sakuta from a car accident and become a heart donor for Shoko Makinohara—a decision later reversed through timeline alterations.

Mai's relationship with Sakuta deepens through shared experiences. She openly expresses love for him and prioritizes their time despite her acting commitments. In "Rascal Does Not Dream of a Knapsack Kid," their commitment is symbolized by a half-joking marriage certificate obtained from Mai's co-stars, which they complete and she retains. When Sakuta grapples with his own Adolescence Syndrome—fueled by unresolved family tensions and fear of being unneeded after his mother's recovery—Mai stabilizes him. She consoles him during his invisibility to others, using the marriage certificate to remember him, and supports his emotional reconciliation with his mother, culminating in a hospital reunion with Sakuta, his mother, and Kaede.

Mai navigates complex family dynamics, resenting her mother for career exploitation but reconciling with her half-sister Nodoka Toyohama after a body-swap incident caused by Nodoka's Adolescence Syndrome. Post-reconciliation, Nodoka befriends Kaede. After high school, Mai takes a one-year break before enrolling at Yokohama City University alongside Sakuta. She balances acting with university life, continuing to cherish her relationship. In the university arc, she encounters new Puberty Syndrome challenges involving a mysterious miniskirt Santa identifying as online singer Touko Kirishima, though her direct role is less prominent. Her journey concludes as a dedicated partner actively pursuing personal and professional goals while maintaining her compassion and resilience.