Mai Kawasumi first appears in the visual novel and anime series Kanon, later featuring in the crossover Kaginado. As a reserved third-year high school student, she secretly battles entities she perceives as demons during nighttime at school, using a sword that damages supernatural foes and breaks bricks yet fails against softer objects like bananas. These activities cause unexplained property destruction, earning her a delinquent reputation among peers and staff. The demons originate from her latent psychic abilities—a harmful side effect of her power to heal and revive life. This ability manifested in childhood when her tears miraculously cured her terminally ill mother, attracting media attention and bullying that forced their relocation. Ten years before her main story, she befriended Yuichi Aizawa during a summer visit. Distraught over his impending departure, she falsely reported demon attacks at a barley field significant to their friendship, though the "demons" were construction vehicles. Her emotional turmoil first activated her power, physically manifesting perceived threats. During high school, her isolation is eased only by her friendship with Sayuri Kurata. When a demon attacks Sayuri, Yuichi aids Mai in nightly battles. Each defeated demon leaves worsening black marks on Mai’s body, later revealed as self-inflicted wounds draining her life force. Learning this truth drives her to attempt suicide by her own sword, but a fragment of her power—personified as a younger version of herself named "Hope"—intervenes and heals her. In Kaginado, her characterization adopts comedic elements: she non-lethally demonstrates combat skills in activities like the Neo Kendo Club’s soccer match. A recurring gag depicts her becoming docile when given beef bowls, contrasting her typical stoicism. Her reserved nature persists; she speaks minimally and struggles with word games like Shiritori.