Kokoro doesn’t go to school. Despite encouragement from her mother and counselor, the preteen (voiced by Ami Touma) feels a wave of anxiety every morning when she thinks about taking those first steps out the door. Instead, she spends the days locked away in her room with little hope for the future in sight.
One day, the mirror in her bedroom begins to glow with a strange energy, and when she approaches, it pulls her into a castle in a fantasy world. There, she meets six middle school students around her age and a mysterious young girl wearing a wolf mask. The masked girl explains the rules: If any one of the children finds a hidden key on the castle’s premises, they’ll be granted one wish. On the other hand, if any of the seven stay in the castle past 5 p.m., they’ll all be eaten by a wolf.
Given several months to find the key and otherwise use the castle at will, the children begin to spend their free time together, forming bonds and discovering why they’ve all been called to this fantasy realm: As it turns out, they all have a lot in common back in the real world. When she returns to her reality, Kokoro’s newfound friendships give her the courage to tackle the trauma that has been keeping her out of school.