Toshikazu Kawaguchi's novel is set in Funiculi Funicula, a cafe in Jimbocho, Tokyo, where a special seat allows customers to travel through time. The cafe is run by chef Nagare Tokita, with his cousin Kazu Tokita serving as waitress and coffee pourer. Time travel is governed by strict rules: Travelers can only meet people who have visited the cafe; nothing done in the past can change the present; one must wait for the seat's permanent occupant, a ghost called the woman in the white dress, to vacate it; one cannot leave the chair once seated; and the journey lasts only until the poured coffee goes cold. Four interconnected stories follow customers who take this journey.
In the first story, "The Runaway," Azami Togo visits the cafe in January 2019, hoping to contact her deceased stepmother, Yumiko Togo. A flashback reveals that 14-year-old Azami ran away from home after her father remarried, resenting Yumiko for replacing her in the household role she assumed after her biological mother died of ALS (amyotrophic lateral sclerosis). During a confrontation in a Kagoshima arcade, Azami shoved Yumiko away and declared they were not blood-related. Years later, now a stepmother herself, Azami understands the pain she caused, but Yumiko has died before Azami could apologize.
Fumiko Kiyokawa, a regular customer and Azami's former colleague, points out that Azami cannot meet Yumiko because Yumiko never visited the cafe. Inspired by Nagare's toddler daughter Miki playing with a toy phone, Fumiko proposes that Azami travel back and phone Yumiko from the cafe's landline. Azami is afraid of what she might hear, but Fumiko insists she needs Yumiko's true feelings rather than a lifetime of uncertainty.
Kazu pours the coffee, and Azami arrives in June 2015, where Kei Tokita, Nagare's late wife, lends her the phone. After a moment of doubt, Azami dials home. When she unconsciously calls Yumiko "Mum" for the first time, Yumiko breaks down crying with happiness. Azami apologizes, tells Yumiko, "Thank you for loving me," and drinks the coffee just before it cools. Afterward, Kazu reflects that she once believed her own mother, who became the woman in the white dress after failing to return from a trip to the past, chose her father over her. She has begun to think, however, that love cannot be ranked.
The second story, "The Patient Man," follows Tomokazu Okishima, who visits the cafe each year on White Day (March 14), a Japanese holiday when men give return gifts to women who gave them Valentine's chocolate. Okishima tells Fumiko about Valentine's Day in junior high, when his quiet crush, Kanna Ozaki, finally gave him chocolate. At the crucial moment, his friend Shigeki Hayashida blurted out that Okishima liked a different girl, a lie Okishima had told to hide his feelings. Both Kanna and Hayashida fled before Okishima could explain. That evening, Kanna was in a bicycle accident on her way home from a cafe, and the resulting concussion erased several years of her memories. Her family transferred her to another school, and she never returned.
Seven years earlier, Okishima had traveled back to Valentine's Day 2012 and found Kanna and her best friend, Misuzu Horie, at the cafe. Before he could clarify the misunderstanding, Misuzu revealed Kanna's feelings aloud, causing Kanna to flee. Okishima drank his coffee, realizing nothing could prevent the accident. Just as his body dissolved into steam, Kanna burst back in and confessed she liked him. With his last conscious moment, Okishima shouted that he would wait at the cafe every White Day until she remembered.
Seven years later, he is still waiting. Fumiko assures him Kanna will come. At closing time, the doorbell rings. A tall, reserved woman enters and asks, "Did you wait?" Okishima replies, "No," and hands her a White Day gift. The clock's minute hand moves forward, signaling that time has begun again for both of them.
The third story, "The Secret," centers on Rikako Kabe, a 32-year-old travel agency manager who asks to travel to the future. Rikako has been diagnosed with cancer and given a 60 percent five-year survival rate. Her boyfriend, Gaku Hanada, a gentle colleague at the same agency, has proposed, but she cannot accept without knowing whether she will survive. She learned about the cafe from Yaeko Hirai, a former regular who runs a ryokan (traditional Japanese inn) in Sendai.
Rikako's plan is to become a regular over the next five years so the staff will recognize her, then travel forward to determine whether she is still alive. Kazu pours the coffee and Rikako arrives in May 2024. A woman at the counter greets her casually, confirming that Rikako's plan succeeded. Kazu returns and greets her warmly, showing no sign of mourning. Koku Shintani, a photographer who has long pursued Kazu, carries his and Kazu's baby, and Rikako notices that Kazu has grown warmer in demeanor.
Nearly leaving without asking, Rikako poses her indirect question: Does Kazu still buy the monthly train timetable? Kazu answers that the current issue would be the last. Rikako understands this means she will die but feels relief at having closure. She returns to the present resolved to refuse Gaku's proposal, believing she cannot ask him to marry someone who will die.
At a Polish restaurant, before Rikako can speak, Gaku slides a ring box across the table and tells her he will not give up. Overwhelmed, Rikako realizes she has been running from her desire for happiness. Remembering Kazu's contentment in the future, she accepts. An epilogue set in April 2024 reveals that Rikako has died. Gaku visits the cafe with their infant son to leave the timetable for his past wife to retrieve, slipping a note inside: "You never gave up, not until the very end. And right up to the end, you looked so happy. Thank you. From your loving husband and son."
The fourth story, "The Father and Son," follows Tsuguo Suga, a 14-year-old whose father, Ryutaro Suga, a chef, died of a heart condition four months earlier. Ryutaro raised Tsuguo alone after Tsuguo's mother left the family due to postpartum depression. Tsuguo came to the cafe because Ryutaro once mentioned eating an exceptional carbonara in Jimbocho, but he fears his father may never have visited. Nagare encourages him to try.
Kazu pours the coffee and Tsuguo arrives in November 2018, six months before Ryutaro's death. The cafe appears empty until Ryutaro emerges from the kitchen, where Nagare has been teaching him to make carbonara. Father and son sit together, and Tsuguo, fighting tears, reveals he has met his mother. Ryutaro is shaken, fearing Tsuguo wants to leave. When the alarm signals the coffee is nearly cold, Tsuguo tells his father, "I'm going to stay with you for ever, Dad," a lie meant to spare Ryutaro grief, since Tsuguo has already agreed to live with his mother. Ryutaro cries and thanks his son, and Tsuguo drinks the coffee and returns to the present.
That night, Kazu receives a message from Koku in France: "Someday, please marry me." For the first time, she replies: "I'll think about it." The novel closes with the quiet observation that their time, too, is moving forward.