Thirty-two-year-old Shoko Hama has spent years fruitlessly searching for a husband and finally decides to give up. After completing a one-year contract as a temporary worker, she books a solo trip to Seoul to celebrate her newfound freedom. On the flight, a handsome younger Korean man, Jobanhi, accidentally drops a bag on her head. As he apologizes and strikes up a conversation, Shoko impulsively lies that she is a married woman. Jobanhi, a photographer who spent time in Japan, proposes that they have a fake affair during her stay. She agrees, and they spend her remaining days together in Seoul, with Shoko continuing to invent details about her fictional husband—even showing him a photo of her brother-in-law.

Back in Japan, Shoko realizes she left her sister Yoko’s wedding ring in the hotel room. The ring was in the coat Yoko had lent her, and she cannot tell the truth. Meanwhile, Shoko discovers that Yoko is also having an affair with a younger mixed-martial-arts fighter named Futa, while Yoko’s husband Kenji remains unaware. Shoko uses the lost ring as an excuse to contact Jobanhi again, and they reunite in Korea. Their relationship deepens, but Jobanhi suffers from a brain tumor. After collapsing, he is hospitalized and later undergoes treatment that causes him to lose recent memories. Shoko learns the truth and returns to Japan heartbroken.

Parallel to this, Yoko’s affair is discovered by Kenji, leading to a confrontation. Yoko chooses to leave her husband and runs away with Futa. Shoko, having resolved to live without lies, travels alone to Iwate Prefecture, a place she associates with Jobanhi. She starts an Instagram account and posts a photo at a train station. Jobanhi, who has recovered but fears his vision may eventually fail, decides to pursue Shoko. He travels to Japan by ship and finds her on the same train. He pretends not to remember her at first, then reveals he knows who she is. He places a glass ring on her finger—a return of the one he gave her earlier. They embrace and begin a relationship free of deception. Both Shoko and Yoko ultimately find happiness by shedding their pretense and facing their true feelings.