Kokoro Anzai is a first-year junior high school student who has withdrawn from school. Suffering severe bullying from a classmate, she becomes a shut-in and is initially withdrawn, submissive, and anxious with no sense of belonging. Her life changes when she discovers a magical portal in her bedroom mirror and is transported to a castle, where a girl in a wolf mask tasks her and six other children with finding a hidden key that can grant a wish. Slowly opening up to the group, she learns each child avoids school for personal reasons, and she forms a particularly close bond with Akiko Inoue. As the deadline for finding the key approaches, Kokoro finds the courage to confide in her mother about the bullying and begins confronting her real-life struggles. She ultimately solves the riddle of the key’s location and, during a critical crisis, makes a selfless wish to save her companions. This act defines her transformation from a frightened, isolated girl into a brave and decisive young woman. Her journey gives her the strength to reconcile with her past and face the future, and she is last seen heading to school alongside Rion Mizumori, another member of the group.