Ayako Takasu wields the supernatural power Beatrice, capable of feats like shooting down satellites and defeating entire military divisions. This earned her the monikers "Witch Beatrice" and "Death Angel." Abandoned by her parents in childhood, who perceived her abilities as monstrous, she was raised in isolation by her prominent politician grandfather within a large mansion under a caretaker's supervision. This abandonment forged an initially cold, asocial nature and difficulty trusting others.

As a student at Tokyo Beatrice University Attached High School, she serves as director of the student committee of discipline. Her demeanor is typically serious and unsmiling, marked by a hot-headed temperament. She readily employs physical reprimands against student council members for intrusive behavior, especially when they spy on her personal life or meddle in her relationship.

Her character evolves significantly after an immediate romantic confession to first-year student Mamoru Yoshimura during their first encounter. This relationship sparks emotional openness, revealing a shy, blushing, and occasionally stuttering side around him. She exhibits clinginess and jealousy when Mamoru interacts with other girls, like Emelenzia Rudiger, yet prioritizes his safety and happiness even during conflicts or threats. Her powers intensify through this bond, and she attributes her combat invincibility to Mamoru's presence.

Her background includes a forgotten childhood meeting with Mamoru during a disaster where her Beatrice-user uncle rescued them. This event initially drew Mamoru to study Beatrice, leading to their academy reunion; neither recalled this shared trauma initially. Her vulnerability surfaces when a Horacle gem nullifies her Beatrice abilities, rendering her powerless and driving a key story arc.

Interactions with the student council and Mamoru's family gradually soften her isolationist tendencies. She assists Mamoru's sister, Itsumi, with cooking and navigates familial dynamics during a home visit, demonstrating growing social adaptability. Her grandfather's political influence intersects with her school life when he publicly interrogates the student body about her relationship status, prompting internal conflict about acknowledging Mamoru.

Her battles against adversaries like Johan Rudiger and Emelenzia, coupled with research into Beatrice's origins alongside her uncle and Johan, expose her to moral and physical challenges. These experiences, including a near-BSoD during temporary separation from Mamoru, deepen her reliance on his support and underscore her evolution from a solitary figure to one integrated within a community.