The Setting Sun charts the collapse of the aristocracy in Japan after World War II. In this immediate post-war moment, Japanese society is undergoing radical change. Through the crises affecting Kazuko and her family, the novel explores the decline of the old order.

Kazuko alludes to the extent of this decline through flashbacks and reveries. She recalls her family’s formerly lofty status in contrast to their current struggles. They must downgrade their house, and leave the urban environment of Tokyo for a more modest place in the country. They must let go of their servants and limit their expenditure. They are not suited to life in Izu; this quickly becomes apparent when Kazuko nearly burns down the entire village because she is not used to disposing of her own firewood. If the local people at one time respected the aristocracy, that respect has gone. Kazuko is chided and pitied by her neighbors, even when she goes from house to house to apologize. The decline in the family’s living conditions is an analogy for the broader decline of the aristocracy in Japan, with Kazuko’s struggles reflecting the struggles of former aristocrats around the country as they adjust to their downgraded status.