Bullied to the point of dropping out of school, Kokoro's days blur together as she hides in her bedroom, unable to face her family or friends. As she spirals into despair, her mirror begins to shine; with a touch, Kokoro is pulled from her lonely life into a resplendent, bizarre fairytale castle guarded by a strange girl in a wolf mask. Six other students have been brought to the castle, and soon this marvelous refuge becomes their playground.

The castle has a hidden room that can grant a single wish, but there are rules to be followed, and breaking them will have dire consequences. As Kokoro and her new acquaintances spend more time in their new sanctuary, they begin to unlock the castle's secrets and, tentatively, each other's.

With the thoughtful whimsy of Before the Coffee Gets Cold, the exquisite textures of A Tale for the Time Being, and the youthful resonance of Your Name, Mizuki Tsujimura paints an intricate portrait of a cycle of loneliness that can only be broken by friendship, empathy, and sacrifice. Lonely Castle in the Mirror is a mesmerizing, heart-warming novel about the unexpected rewards of embracing human connection.