Base-Breaking Character: Taeko, a selfish dilettante who is also capable of deep love and goes through an almost completely undeserved Trauma Conga Line late in the novel.
Designated Hero: Sachiko isn't always the most likeable or morally upstanding of the sisters, but Sympathetic P.O.V. ensures that she's usually treated the most generously by the narrative.
Nightmare Fuel: Sachiko starts out very optimistic, resourceful, level-headed, and maternal. The description of her five-hundred-page slide into crippling depression is...extremely realistic.
Values Dissonance: The Makiokas are generally likeable people who try to do the right thing, but they live in a society in which class barriers are seen as both impermeable and morally praiseworthy, forced abortion isn't seen as a big deal, and the advances of Those Wacky Nazis leave people "overcome with pleasure at the military successes of a friendly nation".
Values Resonance: Taeko, whose sisters see her as a self-absorbed dilettante, comes across as shallow and pretentious even to many readers today.
What Do You Mean, It's Not Political?: The book was shut down by the government in 1943 (serialization stopped, publication forbidden) for, literally, not being political (it's a domestic tale focusing, in the censors' words, on "the very thing we are most supposed to be on our guard against during this period of wartime emergency: the soft, effeminate, and grossly individualistic lives of women"). It's a book that was censored for what wasn't in it.
