Ruth, a writer who lives on a remote Canadian island, finds a lunch box washed up on the beach. Inside it, she is surprised to find an old wind-up watch, some letters written in Japanese, and a diary written in English by a 15-year-old girl named Nao from Tokyo. As Ruth becomes invested in Nao’s story, the novel switches between Nao’s diary and Ruth’s narrative.
Nao begins her diary by saying that she and her reader are both “time beings,” or impermanent creatures. Nao used to live in California but moved back to Japan after her father, Haruki, lost his job. She feels like a cultural misfit in Japan, and she is severely bullied by her classmates who consider her to be a foreigner. Haruki is unable to find a job in Japan, so the family is forced to live in a tiny, rundown apartment. Haruki feels like a failure, and he attempts suicide. He doesn’t succeed, but after the attempt, Nao constantly worries. She is overwhelmed by her problems, and she says that she, too, will die after she writes down the life story of her great-grandmother, Jiko, who is a Buddhist nun. Nao, and most everyone she knows, are wasting their lives—but Jiko uses every moment wisely.
As Ruth reads, she’s concerned about Nao, who has implied that she will kill herself. Ruth quickly flips to the end of the diary and is reassured to see that Nao filled every page. Ruth’s husband, Oliver, says that he thinks the lunch box might have made its way to their island on an ocean drift from the Japanese tsunami and earthquake of 2011. This worries Ruth as well; she begins to search for Nao or her family on the internet, to see if they might be among the dead or displaced. However, she finds nothing. Soon after this, a Japanese Jungle Crow shows up outside Ruth’s house. Oliver finds it very odd that this bird has made its way to their island all the way from Japan; he guesses that it might have ridden the same drift as the lunch box.
In her diary, Nao writes that she spends her summer vacation at Jiko’s temple. After hearing about Nao’s struggles, Jiko teaches Nao zazen meditation—she says it will be Nao’s “superpower” and that it will show her how to really focus on the present. As Nao improves at zazen, she feels empowered and at peace. Jiko tells Nao that she became a nun after her son, Haruki #1, died in World War II. Before Nao leaves Jiko’s temple at the end of summer, Jiko gives her Haruki #1’s watch and a stack of letters that Haruki #1 wrote to Jiko when he was a soldier. The letters document how Haruki #1 was bullied during training, and they show how Haruki #1 came to terms with his imminent death as a kamikaze pilot. Nao idolizes Haruki #1. In comparison, Haruki (Nao’s father) seems like a huge failure to her.
Meanwhile, Ruth worries that she, too, wasting her life. For the past decade, Ruth has tried and failed to write a memoir. Nao’s story is a welcome distraction from writing, and Ruth ends up spending a lot of time trying to make sense of the lunch box’s mysterious contents. Ruth wears Haruki #1’s watch, and she reads the stack of letters that he wrote to Jiko. However, Nao makes no mention of the French booklet, which turns out to be a secret diary in which Haruki #1 wrote his true feelings about the war. Haruki didn’t want to die, and he confessed his plan to fly his plane into the ocean because he didn’t not want to kill other people. Ruth is puzzled about how this booklet ended up in the lunch box.
Nao writes about a horrific incident of bullying: she’s assaulted and almost raped by a gang of male classmates. Nao stops going to school after this incident. She thinks that one of the waitresses at the café, Babette, is her friend—but Babette is only interested in setting Nao up on “dates” with men who pay for sex. Nao is lonely and broken, so she goes along with Babette’s plans. After a particularly sordid sexual encounter with a hentai who hurts Nao, she gets a text message that Jiko is on her deathbed. Nao rushes home to tell Haruki, but when she gets home, he behaves strangely. Nao guesses that he is about to try and kill himself again. She decides it would be pointless to tell him about Jiko and decides to go alone to the temple.
When Ruth gets to this point in the diary, she turns the page and is shocked to see that the last few pages of the diary are blank. She initially saw that all the pages of the diary were written on, so she cannot understand what happened. Nao seems to have decided to kill herself too, and Ruth is very concerned. Oliver tells her that perhaps she must change Nao’s story, since she is a writer. That night, Ruth has a dream that feels very real: she is in a strange place without form or time, and then suddenly the Jungle Crow appears and guides her to Haruki. Ruth tells the Crow that Nao is very worried about him, and that Nao plans to kill herself if Haruki goes through with his suicide. She tells him that Nao is at the train station on her way to see Jiko. The Crow then whisks Ruth off to Jiko’s temple, and Nao finds she has Haruki #1’s secret French booklet in her hand. She places it on the family altar, beside Haruki #1’s picture.
The following morning, Ruth finds that the words have reappeared in Nao’s diary. Nao writes that Haruki came looking for her at the station, and that they went to see Jiko together. Before Jiko dies, she paints a kanji (Chinese character) that translates to “Live.” Nao and Haruki understand that this is Jiko’s final message to them. At the family altar, Nao finds her uncle’s secret French diary and understands his love of life. Haruki becomes emotional when he reads that Haruki #1 planned to fly his plane into the ocean, and he confesses to Nao that he was fired from his job because he refused to sell his software to a defense contractor. Nao realizes that both the Harukis in her life are heroic because they stood up for their ideals, just as she and Haruki #1 are similar because they endured severe bullying. Nao concludes the diary by saying that she is doing well, and that Haruki has started working hard and seems very passionate about a new idea. Neither of them wants to die.
At the conclusion of the novel, Ruth is left with many mysteries—she still doesn’t know if Nao is alive or where she might be. She also doesn’t know how the diary and the other items ended up in the lunch box and reached her shore. Still, these events have taught Ruth that she must pay attention to her present rather than getting weighed down by her past. Ruth realizes that she is happy with her and Oliver’s life on the island, at least for the time being.
