Rintaro Natsuki's grandfather dies suddenly, leaving the grieving teen alone to manage the family secondhand bookshop, Natsuki Books.

An aunt Rintaro has never met arrives to handle funeral arrangements and orders him to close Natsuki Books and move in with her.

A large ginger tabby cat named Tiger appears in Natsuki Books and asks Rintaro to help rescue imprisoned books.

Tiger leads Rintaro through a magical corridor into a grand mansion, where they meet the Imprisoner of Books.

Rintaro challenges the Imprisoner of Books, arguing his glass-cased collection proves he loves himself, not literature.

The Imprisoner's convictions shatter, his glass cases break open, and the freed books transform into birds and fly away.

Tiger leads Rintaro and classmate Sayo Yuzuki into the second labyrinth, the sterile Institute of Reading Research.

Rintaro fast-forwards a Beethoven cassette to prove that rushing great art destroys its soul, defeating the Mutilator of Books.

Tiger announces a third labyrinth and leads Rintaro and Sayo to the skyscraper headquarters of World's Best Books.

Rintaro defeats the Seller of Books by arguing that his obsession with sales betrays a hidden love for literature.

Tiger confesses that his true purpose was to help Rintaro overcome his grief, bids farewell, and disappears.

Tiger reappears on Rintaro's moving day with urgent news that Sayo has been kidnapped by an unforeseen fourth labyrinth.

Rintaro enters the final labyrinth and confronts an elderly woman in a desolate replica of Natsuki Books, declaring that books cultivate empathy.

The three previous labyrinth masters reappear to endorse Rintaro's philosophy, moving the elderly woman to release Sayo.

Three months after his adventures, Rintaro decides to stay and run Natsuki Books, having built a meaningful new life.

After Rintaro Natsuki's grandfather dies and his aunt orders him to close the family bookshop, a talking cat named Tiger arrives and recruits Rintaro to defeat three antagonists who corrupt books for vanity, efficiency, and profit. Rintaro conquers each labyrinth by defending his grandfather's philosophy of literature, growing bolder with each victory. After Tiger bids farewell, a fourth crisis erupts when a mysterious figure kidnaps Rintaro's classmate Sayo, forcing him into one final battle. There, Rintaro faces the despairing soul of a neglected book and wins by declaring that literature's true power is empathy. The three former antagonists endorse his belief, Sayo is freed, and Rintaro ultimately chooses to stay and continue his grandfather's legacy.

The headline quest from a bookshop in mourning to its triumphant revival.

Rintaro oversees a closing sale at Natsuki Books while skipping school, overwhelmed by grief after his grandfather's death.

Senior student Ryota Akiba visits Natsuki Books to express sadness at its closing and urge Rintaro to return to school.

Class president Sayo Yuzuki visits Natsuki Books to deliver Rintaro's homework, scolding him while showing genuine concern.

Rintaro sits alone in the darkening shop when the front-door bell chimes, though no one has entered.

Tiger quotes Antoine de Saint-Exupéry's The Little Prince to establish that essential truths are felt, not merely seen.

After returning from the first labyrinth, Rintaro begins cleaning Natsuki Books, resuming his late grandfather's daily routine.

Tiger reappears the morning after the first labyrinth to congratulate Rintaro on his victory, then promptly vanishes.

Sayo Yuzuki insists on joining the second labyrinth mission, refusing to let Rintaro face unknown danger alone.

The Mutilator of Books reduces Osamu Dazai's story "Run, Melos!" to the single dismissive sentence "Melos was furious."

Sayo returns from the second labyrinth with no memory of its conclusion and questions Rintaro about his failure to pack.

Ryota Akiba encourages Sayo to check on Rintaro, prompting her visit before the third labyrinth mission begins.

Tiger is refused entry to the World's Best Books skyscraper, forcing Rintaro and Sayo to confront the Seller alone.

From the Seller's window, Rintaro and Sayo watch thousands of books hurled from surrounding buildings into a vast wasteland.

Rintaro's aunt visits him on his scheduled moving day before Tiger returns with news of the fourth labyrinth.

Rintaro hears Tiger's voice one final time and glimpses the cat disappearing over a fence as the shop bell rings.

Before any magic begins, Rintaro's world is defined by small but meaningful visits: a senior who urges him back to school, a class president who delivers his homework, and the unsettling sound of a bell with no one behind it. Tiger's early philosophical wit and Sayo's courageous insistence on joining the adventure mark the missions' turning points. Details such as the Mutilator's shocking reduction of a classic story to a single sentence and Sayo's eerie trance reveal the true stakes of each labyrinth. Practical realities—Tiger being barred from a corporate skyscraper, books raining into a wasteland, and Rintaro's aunt arriving on moving day—ground the fantasy in consequence. The pool closes with Tiger's final whispered farewell, a quiet bookend to all the magic.

The supporting moments that quietly shaped Rintaro's journey.

Rintaro experiences his grandfather's funeral with profound detachment, feeling as though he is watching a badly performed play.

After returning from the first labyrinth, Rintaro invites Sayo into Natsuki Books for tea for the first time.

Sayo arrives at Natsuki Books, is shocked to see and hear Tiger, and demands to join the second labyrinth mission.

The Mutilator of Books demonstrates his streamlining method by physically cutting up a classic novel with scissors as Beethoven plays.

Sayo begins to fall under the Mutilator of Books' spell, her expression turning blank and vacant as he speaks.

Rintaro recalls his grandfather's teaching that the struggle and effort of reading are themselves part of its true value.

Sayo visits the shop and Rintaro confirms that his scheduled moving day is only two days away.

The Seller of Books declares that books are merely expendable goods and that sales are the only measure of worth.

Sayo grips Rintaro's arm and tells him the Seller of Books does not believe half of his own arguments.

Tiger reveals to Rintaro that he is the soul of a book that Rintaro's mother used to read to him.

Tiger explains that while a cherished book can gain a soul, a neglected book's soul can become warped and malevolent.

Tiger leaves Rintaro alone to face the elderly woman at a desolate replica of Natsuki Books.

The elderly woman shows Rintaro visions of the three former labyrinth masters suffering hardships as a result of his actions.

Rintaro pursues the elderly woman into a dark corridor, driven by his determination to rescue the kidnapped Sayo.

Sayo invites Rintaro out on a date, and he offers her heartfelt thanks for all her support.

Rintaro's journey begins with emotional numbness at his grandfather's funeral and slowly thaws through a series of decisive moments and startling discoveries. Key turning points include his first social breakthrough—inviting Sayo for tea—and Sayo's bold entry into the second labyrinth, where her near-enchantment forces Rintaro to act with urgency and inherited wisdom. In the third labyrinth, Sayo's perceptiveness provides the crucial insight that breaks the Seller's defenses, cementing their partnership. The fourth labyrinth delivers its deepest revelations: Tiger's true identity as the soul of a cherished book and his warning that neglect can corrupt even beloved stories into something malevolent. Rintaro's desperate pursuit through a dark corridor and Sayo's invitation for a date mark his complete transformation from isolated mourner to someone capable of connection.