The story is a fantasy featuring tiny people, like many children's books in English and Japanese literature. Inui in an afterword mentions being enthralled by a book on fairies by Yeats; and the little people here are in fact British fairies. MORIYAMA Tatsuo's English teacher brought the little people with her when she came to Japan as a young woman. Now, in 1914, she is returning to England and asks Tatsuo to look after them, giving him a blue glass in which they must be given milk every day. Tatsuo installs them in an unused bookroom in a tree shadowed corner of the house. And there they stay, provided with milk first by Tatsuo then by later generations of the family.
But the core of the story is the experience of life in wartime Japan, which the little people first witness as two men come into their room, pulling volumes from the shelves to pile up on the floor as they search through the books.
"The books here are mostly just the children's books."
"Madame, in your house is this the kind of book your children read?" said one of the men, pushing a black covered book in German in her face.
"Ah. Kropotkin. That's .... well yes, that is my father in law's -"
"For now we'll take it with us to the station for consideration."
The story on the one side centres on the young daughter of the family, Yuri, who is evacuated to the countryside and must try to find the milk that the fairies in her care need to live, on the other on the fairy family themselves, the parents, Balbo and Fern, who are accustomed to rely on the human family, and their children Robin and Iris, who gradually start exploring the world outside. The depiction of the wartime mood in Japan is fairly bitter: Yuri's father is imprisoned for unpatriotic sentiments; but one of her brothers thinks he deserves it for betraying the country and that Yuri is similarly unpatriotic in giving milk to the fairies. In the countryside where Yuri is sent, she soon becomes isolated, since the other children's families regard her family with disapproval, in particular the mother of her friend, who is proud of the her other sons, who have lost their lives in the war. And sickness and the difficulty of getting milk lead to a bitter parting with the fairies in her care. The expanding horizons of Robin and Iris are more optimistic, as they make friends first with a pigeon then with a Japanese fairy. But although the book's ending is not exactly unhappy, and there is a reconciliation of sorts between Yuri and the fairies, the reader is likely to be left a little melancholy and thoughtful.