The Sound of the Mountain delves into the life of Shingo, an elderly Japanese businessman, capturing how the daily occurrences around him subtly shape his inner world. As Shingo grapples with the slow onset of senility, his memories of the past grow sharper, contrasting with his desire to retreat from the chaos of everyday existence. However, his hopes for peaceful reflection are dashed when he is drawn into the ordinary but troubling affairs of his family, particularly the strained marriages of his son and daughter.

The Marital Struggles of Shuichi and Kikuko

Shingo's son, Shuichi, is entangled in an affair with a war widow, causing him to neglect his wife, Kikuko, who resides with Shingo and his wife, Yasuko, in Kamakura. The visible tensions in Shuichi and Kikuko's marriage disturb Shingo deeply. He is dismayed by his son's reckless behavior and worries even more about the welfare of his gentle and beautiful daughter-in-law. Shingo's disappointment in his son's actions is compounded by a deep concern for Kikuko, whose delicate nature makes her particularly vulnerable.

Fusako's Return to the Family Home

Adding to the family's turmoil, Shingo's daughter, Fusako, faces her own marital upheaval and may have suffered physical abuse at the hands of her husband. After much indecision, Fusako decides to return to her parents' home in Kamakura with her two children. Once there, she distances herself from her responsibilities, leaving her children in Kikuko's care, and seems resigned to a life of bitterness and dissatisfaction. Despite Shingo's attempts to inspire Fusako with a renewed sense of purpose, his efforts fall short.

Shingo's Views on Marriage

Despite the challenges his children face, Shingo clings to a hope that their marriages will endure through the trials they face. For Shingo, marriage represents an avenue not necessarily for happiness, but for a life imbued with meaning and morality. This belief, subtly woven into his actions and words, reflects the cultural contrasts between Japanese and Western perceptions regarding social duty versus personal fulfillment. Although Shingo's own marriage to Yasuko is fraught with dissatisfaction, he accepts it as an unchangeable reality, akin to the inevitability of death.

Kikuko's Secret and Shingo's Dilemma

Without alerting the family, Kikuko becomes pregnant but chooses to have an abortion for reasons she keeps to herself. Shingo, upon discovering this secret, is initially shocked yet ultimately forgiving, attributing the unfortunate situation to Shuichi's cruelty. He also feels a burden of guilt for not having intervened sooner, sensing a degree of culpability for the outcome. The situation becomes more complex when Shingo learns that Shuichi's mistress is also pregnant, prompting him to encourage her to consider an abortion. However, he is later haunted by the moral implications should she comply with his request.

Hopeful Reconciliation and Future Uncertainties

As Shuichi and his mistress drift apart, she relocates to the provinces, seemingly intent on having her child. Meanwhile, signs of reconciliation appear between Shuichi and Kikuko, rekindling Shingo's hope that their marriage may indeed survive. Fusako, however, remains estranged from her husband, who has barely survived a suicide attempt, leaving her future uncertain. The novel concludes quietly, with the family sharing a humble dinner of three pieces of trout among seven people. In that moment, Shingo suggests a family visit to the countryside to see the maples, momentarily setting aside the family's undercurrents of discord.