Series by 辻村深月

Anzai Kokoro, a middle school girl who has withdrawn from school due to bullying, spends her days isolated at home until a glowing mirror in her room transports her to a mysterious castle. There, she meets six other kids—each facing their own struggles—guided by a wolf-masked girl who gives them until March to find a key that grants a wish. As Kokoro bonds with her new companions, including the quiet Rion and the cheerful Aki, this heartfelt tale blends mystery, friendship, and healing, following a group of teens uncovering their pasts and finding strength in each other within the enigmatic walls of a lonely castle.

On a snowy morning, eight high school students arrive at their school, expecting a normal day—only to find themselves trapped in an eerily empty building. The doors won't open, the windows won't break, and the clocks are frozen at 5:53. As they grapple with their isolation, the group begins to realize they can't remember the name or face of a classmate who took their own life during the school festival months ago. With time standing still and an unsettling presence lurking, they must confront their past, their guilt, and the mysteries binding them to this frozen moment.