Mei Sagara, a third-year Miryuin Private Academy student, presides over the Lyrical Sister Café—a roleplay haven where patrons assume sibling personas. Her witch-inspired aesthetic features glasses and mystical attire, reflecting her calculated persona. Cast aside by her birth parents as a toddler when her extraordinary mathematical intellect surfaced, she was raised by a professor and his wife. Her adoptive mother’s café became her childhood workplace, later sold after the mother’s death. Mei reclaimed it through profits from her entrepreneurial ventures, reestablishing it as both enterprise and sanctuary for fabricated kinship.

Her entanglement with Shogo Mikadono originates from a childhood pact with his illegitimate sister. Sworn to shield the girl from societal scorn, Mei masquerades as Shogo’s sister, deliberately obfuscating his search. She demands he prove his worth as a brother through trials, delaying truth until he demonstrates unwavering dedication.

A shrewd strategist, Mei integrates theatrical flair with commerce, outfitting staff with emotion-sensitive feline accessories to enhance the café’s moe-centric allure. Her exchanges with Shogo double as assessments, tasking him with challenges that scrutinize his commitment to familial duty.

Central to her machinations is a phone mirroring Konoe Tsuruma’s—a deliberate red herring to sustain her deception. Though her arc culminates in a conditional agreement to unveil the sister’s identity, the revelation unravels familial intricacies exceeding Mei’s initial understanding, complicating the bonds she sought to orchestrate.