Kokoro Anzai, a first-year student at Yukishina Junior High School, finds herself in a challenging reality where she is overwhelmed by relentless bullying, causing her to dread attending school. Her situation only worsens as she feels increasingly out of place, especially during a child development support class, ultimately leading her to completely avoid returning to school. However, her life takes an unexpected turn when she discovers a mysterious magical portal hidden within her room's mirror. While exploring this strange new world, she is unexpectedly pulled through the mirror and transported to a magnificent castle situated on a secluded island surrounded by glistening waters.
Upon her arrival, she is greeted by an enigmatic girl donned in a wolf mask, who introduces herself as the Wolf Queen. This intriguing figure unveils a peculiar challenge for Kokoro, alongside six other children—Subaru Nagahisa, Aki, Rion Mizumori, Fūka Hasegawa, and Masamune. The Wolf Queen refers to them as Little Red Riding Hoods and instructs them to embark on a quest to discover a hidden key within the castle. This key holds the potential to unlock a room where a wish can be granted, but there’s a catch: they must uncover it by the rapidly approaching deadline of March 30 of the following year. If any of the children manages to make a legitimate wish, their desires will be fulfilled, but the shocking trade-off is that they will forget their time in the castle entirely. The Wolf Queen sternly cautions them: if they remain in the castle past 5 PM, a dire fate awaits, as a wolf will come to eat them.
In the days that follow, the seven children find camaraderie as they navigate their mysterious surroundings, spending substantial time together and occasionally searching for the elusive key. As time flies, nearly a year passes, yet their efforts bear no fruit. During this period, Kokoro learns that the others, with the exception of Rion, are from her own school, each harboring their reasons for avoiding school as she steps into a new chapter of self-discovery. They devise a plan to meet at school, only to uncover a shocking reality: they exist in separate worlds. This astonishing revelation leads Masamune to theorize about the possibility of parallel universes, a notion swiftly challenged by the Wolf Queen, who denies the theory outright.
As the critical deadline looms closer, the urgency to find the key increases, yet their search remains futile. Meanwhile, Kokoro takes a significant step by confiding in her mother about the bullying she faces, with the help of her supportive teachers actively working to address the situation. The others also embark on their own journeys of healing and courage.
On the penultimate day of their quest, Kokoro stumbles upon a curious illustration titled "The Wolf and the Seven Young Goats." This discovery proves to be pivotal as she pieces together that it serves as the key’s clue to its location. However, upon returning home, she is heartbroken to find the mirror shattered into countless pieces. The grim news from the others reveals that Aki inadvertently broke the cardinal rule and stayed past the designated time, leading to a tragic outcome where the remaining children are consumed by the wolf due to their adherence to the rules.
Desperate to rescue her friends, Kokoro traverses through the remnants of the shattered mirror. With the clues gained from the illustration in hand, she embarks on a quest to uncover the key, gradually piecing together fragments of her friends' memories. To her dismay, she learns that each of them grapples with their struggles, particularly with bullying. Caught in a cycle of bullying and harassment, Aki found solace within the castle’s walls. In a moment of profound realization, Kokoro uses her wish to save her friends, ultimately leading to Aki’s revival, where they all experience a beautiful reconciliation.
As the time draws near for them to return, they come to a poignant understanding: they are all from the same universe, merely existing in different timelines that span over four decades. In a heartfelt moment of unity, they carve their names into the castle wall as a keepsake before bidding each other farewell. After every one of them has crossed back through the portal, Rion encounters the Wolf Queen, leading to the revelation that she is, in fact, his late sister, Mio. With the mask removed, she tenderly bids him farewell.
Back in her own timeline, Kokoro experiences a joyful reunion with Rion, as they walk together towards school, united in a newfound strength and hope for the future.
