くらやみの谷の小人たち (The Little People of the Valley of Darkness, 1972) by INUI Tomiko is a sequel to 木かげの家の小人たち(The Little People of the House in the Tree's Shadow, 1959), which I wrote about earlier. The first book combined a fantasy story, a Japanese family caring for English fairies, with a depiction of Japan in wartime, the people's lack of food and their intolerant patriotic fervour. The book had spanned more than one generation of the Moriyama family, and the sequel similarly takes the story through to the next generation, represented in particular by Jun, the son of Shin, the jingoistic middle brother of the first book.
In a sense 木かげの家の小人たち leaves a lot unsettled, but it's not clear that it really needed a sequel. The tentative half resolution is what one might expect to come out of the experiences the characters had gone through, and the uncertainties that face them feel like the author's intention. Inui explains in the afterword that she had started on a sequel in 1967 (as she announced in the afterword to an edition of the first book), but it had taken that long to finish it. Still, the long gap means that the way of looking at things seems to have changed from book to book (like Ursula Le Guin's Tehanu). The first book had very few "adventure" elements; but the sequel is largely an adventure story, although it has some parts devoted to description or consideration of the period it describes, in particular of the first hungry years after the war, but also the reaction of the Moriyama family to changes in Japanese society and attitudes. In addition some of the new ideas about the blue cup from the first book seem to involve a rather ruthless rewriting of the original concept (indeed they undermine the major plot driver of the first book).
The Japanese kobito, Amanejaki, had been one of the more energetic characters from the first book, which ended with Iris and Robin leaving their parents and joining him in his home in a wood near Lake Nojiri. The sequel follows their adventures and brings in a large cast of Japanese kobito, most of them apparently spirits of Japanese flowers. These live in a dark underground world, which is dominated by the hostile spirits of various trees. The smaller spirits are searching for the spring of "The water of life", and their enemies are planning to exterminate them by bringing the "river of death" into the valley. This is a bit too much of a typical fantasy battle of good and evil; and only one character on the "evil" side is really given any personality or story.
The depiction of the river of death's effects perhaps reflects concerns about radiation sickness (the book mentions the atom tests on Bikini Atoll and the effects of the dust from the explosion on wildlife and on a Japanese fishing ship); but it presumably symbolises something more like an orientation towards war. Iris, as in the first book, is knitting as a prayer for peace in the world. This does not stop the good party from fighting against their enemies, although actual fights make up only a tiny part of the book.
If this sounds like an unnecessary and inferior sequel, it is still a well written book, with many impressive episodes.