Leona Miyamura is the older sister of Toranosuke Miyamura and a former member of the Supernatural Studies Club at her school. A year before the main events of the story, she and her close friend Haruma Yamazaki, with whom she shared a deep bond, formed the club with the goal of locating all seven witches rumored to exist on campus. They succeeded in discovering six of them, but the identity and power of the seventh witch remained unknown. When Leona eventually learned the name of the seventh witch and the nature of her ability—a power that can erase specific memories from other people—she became terrified of being targeted. In response, she stopped attending classes, withdrew from normal school life, and secluded herself in a hidden room on campus. There she spends her time typing on a computer, wary of any intruders and ready to defend herself by throwing scissors like knives.

Leona carries a mysterious and old-fashioned air, and she often comes across as cold, distant, and even violent toward those who approach her unexpectedly. This guarded behavior stems from her intense fear of the seventh witch’s memory wipe, which she believes could destroy the personal connections and knowledge she values. Despite her withdrawn nature, her underlying motivation is not simply self-preservation; she cares deeply about the people from her past, especially Haruma, who urged her to flee when he learned the full extent of the seventh witch’s power. Her love for Haruma was a driving force behind their shared research into the witches, and it is this bond that eventually encourages her to re-engage with the world.

Within the story, Leona acts as a key informant and guide for Ryu Yamada. After he and his allies learn of her existence, she reveals the name of the seventh witch and explains why she went into hiding. Although initially reluctant, she later meets Yamada again with the help of Nene Odagiri and informs him that if all seven witches gather together, a wish can be granted. Her role shifts from a reclusive figure to an active contributor who helps the protagonists navigate the witch‑related mysteries. Over the course of her appearances, Leona gradually overcomes some of her fear, showing growth by trusting Yamada with critical information and stepping out of her self‑imposed seclusion to assist him.

Leona has no supernatural abilities of her own. Her notable traits are her deep knowledge of the witches and their powers—gained through months of research alongside Haruma—and her resourcefulness in defending herself with scissors. Her development is marked by moving from a state of paralyzed fear and isolation to one of cautious cooperation, driven by her lingering affection for Haruma and a desire to see the truth about the witches finally uncovered.