In 19th-century Japan, Shinnosuke is visited by Shizu and her sister Oyū to see if Shizu is a suitable marriage prospect for him. Yet, Shinnosuke is more fascinated by the older Oyū. Tradition forbids the widowed Oyū from remarrying as she has to raise her son and future heir of her deceased husband's family. So, Shinnosuke and Shizu marry as a means for him and Oyū to be as close as possible. When Oyū learns that Shizu declined to consummate the marriage as a sign of respect for her older sister and the affection between her and Shinnosuke, Oyū scolds her. Also, rumours about the true nature of their relationship start to spread, prompting Oyū to create distance between them. Later, Oyū's son dies, and she has to leave her husband's family, while Shizu dies shortly after giving birth to her and Shinnosuke's child. Shinnosuke, whose family has lost its fortune, leaves his child with the remarried Oyū and asks her in a letter to raise the child as her own.
