A chronic asthma condition prevents 13-year-old Nanami from joining sports or hanging out with her friends after school. However, she loves reading and is happy to spend most of her free time in the library, cocooned by stacks of books in all directions. One day, Nanami notices that, despite the library remaining as deserted as ever, her favorite Arsène Lupin, Gentleman Burglar, Anne of Green Gables and other classic works of literature are gradually disappearing from the shelves. When she alerts the library staff, no one seems to take her seriously. Her concerns are brushed off as a product of her imagination. Just as Nanami is about to go back to her reading, she spots between bookshelves a suspicious man in a gray suit. She follows the man hoping to find out what he is up to, but an asthma attack cuts the chase short and all that is left behind is a mysterious light filtering through the library’s familiar passageways. That’s when, to the delight of readers all over the world, talking tabby cat Tiger comes once again to the rescue. 

Will Nanami and Tiger overcome the challenges of the dangerous adventure ahead? Why are faceless gray soldiers burning books in a stone castle? And what happened to Rintaro, the socially withdrawn hero of the first novel? In the age of book banning, Sosuke Natsukawa urges us not to underestimate the power of great literature and to be prepared to defend our freedom to choose.