The novel flashes back to Japan in 1945.

Six-year-old Hiroshi loves going to school. He comes from a poor family, lives in a seaside town, and is the top student in his class. Because their food supplies are heavily rationed, Hiroshi and his friends frequently shoplift vegetables from the market. He brings home his yield to support his parents and his younger siblings. Although Hiroshi’s parents do not share in his enthusiasm for Imperial Japan, he sees their work as important, especially since his father does manual labor for the Japanese war effort. Hiroshi learns how to use a bayonet, harvest peas, and fashion a head covering to protect him during bombing raids.

One afternoon, US soldiers parade through the town to announce that Japan has surrendered to the United States, signaling the end of World War II. Hiroshi can neither read nor recognize the Korean flag as it passes by, prompting his mother’s friend to shame him for not knowing his own heritage. When Hiroshi is unaffected by the news of Korea’s liberation, his mother reminds him that he is Korean and that his birth name is Seok.

Hiroshi is disappointed by the revelation of his Korean heritage, which shatters his imperial idealism. Following the end of the war, the school undergoes massive reforms. Hiroshi asks his sensei for a world map to look for his parents’ home island, Jeju. Because the map reflects occupied Korea, Jeju is labeled Saishū. Fearing that Hiroshi’s parents will force him to return to Korea, the sensei encourages Hiroshi’s to stay in Japan, citing Hiroshi’s potential to carry on the empire’s ideals.

Hiroshi’s parents join a committee of Koreans living in their area and arrange for Hiroshi’s transfer to a Korean school. The school is soon closed by the Americans on suspicion that the committee is run by Japanese Communist Party sympathizers. Hiroshi discovers that his father is a Communist who was convinced to emigrate from Jeju during the occupation, when the party advocated for fairer wages and working conditions for Koreans in Japan.

In 1948, Korea is divided in two: The North is occupied by the Soviet Union and the South by the United States. Tensions rise among Korean communities in Japan, provoking the United States to leverage its military power against Koreans who protest its rule. Hiroshi is instructed to write a letter asking the United States military to allow his younger sister, Soonja, to enter Korean school. Hiroshi reluctantly obeys, and the effort proves successful. His parents’ committee soon joins the Organization, a group concerned with the welfare of Koreans residing in Japan. The Organization flies the flag of North Korea, now known as the Democratic People’s Republic of Korea (DPRK).

In 1952, Hiroshi enters high school. His parents hope that he will transfer to a Korean school, but he is again discouraged by his old sensei, who worries that Korean education will ruin Hiroshi’s university opportunities. Hiroshi ultimately declines to transfer. As a compromise, he agrees to his parents’ other request, which is to use his birth name, Seok. Japan’s major universities reject Seok, who instead enrolls at Tokyo Technical College. He feels alone at home and at school; unable to share his disappointment in himself with anyone else, he refocuses his energies into his studies.

Seok is shocked when his parents announce that they will be moving to the DPRK, drawn by an offer to subsidize Koreans who voluntarily return. Seok suspects that the offer may be a scam, but that does not stop his parents from acquiring their transit documents. Seok rushes home to convince them to see Japan as their home, but he cannot argue against their treatment as second-class citizens in Japan. Soonja elopes with her Japanese boyfriend. Seok’s other siblings elect to go with their parents. Seok bids his parents a bitter farewell, gives his siblings money to help them settle, and assures them that they will always have a home with him in Japan.

Days later, Seok receives a letter from his sister Yeonja. The family is still in transit at the port city of Niigata. Everyone is expected to affirm that they are repatriating to Korea of their own volition. Yeonja’s next letters, which arrive in increasingly delayed intervals from North Korea, include requests for various items, such as vegetables, shoes, and soap. The vagueness of the letters makes Seok skeptical of their validity. Nevertheless, he believes Yeonja’s assurances that their family is fine and acquiesces to her requests. He wonders why Yeonja is the only person writing to him.

After graduation, Seok jumps at a chance to apply for a graduate program in the United States. Before he leaves, Seok visits Soonja, who has become unhappy in her marriage. He tells her to take up the correspondence with their family, who he doubts will ever return.

During her travels through the Middle East with a man named Adrian, 19-year-old Anne discovers that she is pregnant. Adrian drew Anne away from her life in Ohio with his intelligence and charm, which was a stark contrast to the loneliness she felt as the youngest member of her large family. Upon learning of her pregnancy, Adrian accuses Anne of deceiving him. Anne returns to the United States, where she carries her pregnancy to term in a Massachusetts boardinghouse. After giving birth, Anne turns custody of her son, Tobias, over to Adrian and his wife. Anne will remain updated about Tobias; once he is old enough, Tobias will be told about his mother.

Anne works as an assistant to Dr. Louis Grassi, an English professor at Smith College. Dr. Grassi arranges Anne’s informal education, recommending books. In 1963, through Dr. Grassi’s professional network, Anne meets a Japanese electrical engineering doctoral student named Serk (a mispronunciation of Seok) Kang. Anne and Serk enter a passionate relationship, connecting over sex and their respective experiences of solitude. Anne feels neglected by her parents and siblings. Serk claims to have no family, which Anne does not believe.

Serk’s scornful personality reflects his resentment over being patronized as a foreigner. Anne is glad to be Serk’s confidante. Three summers into their relationship, they marry. When Anne asks about inviting his family to the wedding, Serk gets angry. Anne resolves not to ask about family again.

Serk and Anne move to Rolling Prairie, Ohio. One year later, Anne gives birth to Louisa. Louisa is precocious. Serk often gets angry with Anne for being careless with Louisa. On one occasion, Serk rebukes Anne for taking Louisa to swimming lessons. Anne argues that the lessons might save Louisa from drowning. She soon realizes that Serk does not know how to swim.

In 1976, Adrian calls Anne to ask her to meet Tobias. Tobias is 16, having behavioral issues that Adrian finds difficult to manage, and is aware that Anne is his biological mother. Stunned, Anne accepts Adrian’s request.

Anne decides to take Louisa and Tobias to a strawberry farm. She tells Louisa that Tobias is a family friend, which Louisa does not believe. Anne is afraid of what Louisa might do if she realizes who Tobias really is. Tobias proves to be a reserved teenager, though Anne worries that this masks his resentment for her.

At the farm, Anne cautions Louisa not to get too close to the electrified fence that separates the strawberry field from the horse pasture. Tobias disregards this warning, reaches out to pet an approaching horse, and is electrocuted. He is taken to the emergency room. Later, when Anne asks Louisa to keep the events of the day secret from Serk, Louisa presses her to explain who Tobias and asks if Tobias is dead. On the way home, Louisa gets upset that the strawberries they’ve picked have leaked through the packing box. Anne fails to reassure Louisa that she can make preserves from their yield.

Tobias’s grandmother calls Anne to tell her that Tobias had to return to the hospital. An X-ray revealed a tumor in his brain. Anne lies to Serk that one of her friends needs to go to the hospital, so that she can go to see Tobias, who is in an induced coma. She thinks about what she would say to him, but everything she thinks of feels too trite. She prays for his survival.

When Anne gets home, Serk rebukes her for her negligence. Louisa ate some of the strawberries, but because they were already spoiled, she vomited. Serk angrily drives away. Louisa apologetically explains that she thought Tobias was dying; Anne assures Louisa of Tobias’s well-being. Louisa adds that she kept Anne’s secret from Serk.

Tobias survives the surgery and returns home, where his behavior returns to normal. Adrian declines Anne’s request to visit Tobias. Anne wonders if Tobias told Adrian how he ended up in the hospital, or if he forgot what had happened. She regrets that the only day they spent together only exists in her memory, but gives up further attempts to reach Tobias.

After Louisa gets sick from eating spoiled strawberries, Serk goes to the library. His anger towards Anne was exacerbated by the obvious lie she told him. Serk wants to stay out to punish Anne for her negligence. The library is closed, so Serk goes to his office.

In her latest letter, Soonja claims that their father has fallen ill and requires transit to Japan for treatment. Soonja needs Serk to return to Japan, so that he can finance their father’s treatment with his American wealth. Serk finds her letter too vague and wants more details about their father’s illness. This irritates Soonja.

Early during his stay in the United States, Serk was interrogated by government officers about his connections to the Communist Party. He denied any connection whatsoever, but now worries that Soonja’s letters may inadvertently expose their family’s affiliation with the DPRK-associated Organization. Meanwhile, Serk has been asked to take another faculty member’s place in an exchange program with their sister college in Japan. Though he is reluctant to accept the offer, Serk sees it as an opportunity to honor Soonja’s request.

Serk has been seeking refuge in the Children’s Room of the library, which is never used by anyone except a librarian named Barbara. Once, Serk asked Barbara about letting Louisa study outside her birth country. Barbara reassured him that children adapt more quickly to new environments than adults do.

The previous August, Serk and Anne were introduced to a Korean graduate student named Tae-Min Lee, who came to the United States with his wife. The two couples became friends. Sometime later, Louisa found a letter addressed to Serk with North Korean stamps. This upset Serk, who interpreted the letter as evidence that Tae-Min was an intelligence agent trying to coerce him. When Tae-Min revealed that he had received a similar letter, Serk apologized for his rash judgment. Sometime later, Tae-Min mysteriously vanished. Weeks passed without Tae-Min returning home. Soon, Mrs. Lee disappeared as well.

In his response to Soonja, Serk writes for more time—he needs to prepare his American family members for the move to Japan.