かがみの孤城

Upon enrolling in the local middle school, Kokoro loses the courage to actually attend. While isolating herself in her room, her bedroom mirror begins to glow, allowing her access to the mirror castle, where she meets six other children who are supposed to be in school and a younger girl in a wolf mask.

Early on, the novel places the pieces that will be set into motion later on. As a result, the actual story builds very slowly in the first half, but once all the pieces slowly fall into place, it becomes clear that this is really the only way this story could have been told. Over the last 200 pages I couldn't put it down at all!