In Kōchi, Taku Morisaki, Nobuo Tobita, gets a call from his friend Yutaka Matsuno, asking to meet at their old high school. They find Yutaka with a striking transfer student, Rikako Muto, whom Yutaka has been asked to show around. Rikako is academically gifted and excels in sports, but she carries an air of arrogance. Taku suspects she might be unhappy about leaving Tokyo.
On a school trip to Hawaii, Rikako asks to borrow money, and Taku lends her ¥60,000, with Rikako promising to repay and quietly warning him not to tell anyone. The gesture leaves him with a sense of obligation rather than admiration, and Rikako’s cool assurance leaves a trace of doubt about her reliability.
Back in Kōchi, Rikako makes a new friend, Yumi Kohama, Kae Araki. Rikako has not returned the loan, and Taku wonders if she has forgotten it. Out of the blue, a distressed Yumi contacts Taku, explaining that Rikako duped her into going to the airport under the pretense of a concert trip, only to discover their real destination is Tokyo, with tickets paid for using Taku’s money. Hurrying to the airport, Taku ends up traveling to Tokyo with Rikako in place of Yumi.
When Taku and Rikako reach her father’s residence, they discover Rikako’s father has already found a new lover. Rikako’s father thanks Taku, repays the loan, and even arranges a room for him at the Hyatt Regency. Rikako, disappointed in her father, explains that during fights she had always sided with him, but now realizes that he might not be on her side after all. Taku offers his bed, and he finds himself sleeping in the bathtub, trying to brace against the discomfort of a situation that feels more complicated than romance.
The following day, Rikako kicks Taku out so she can change clothes to meet a friend for lunch. After wandering through Tokyo and catching up on some sleep at the hotel, Taku receives a call from Rikako asking to be rescued from her former boyfriend, Okada. When he arrives, he becomes frustrated by the conversation and chastises Rikako and Okada for being “bores.”
Back home, Rikako ignores Taku but tells her friends they spent a night together. Yutaka confesses to Taku that he had told Rikako he loved her, only to be brutally rejected, prompting Taku to confront Rikako in the classroom. They quarrel in the corridor, where she slaps him and he hits her back.
The autumn cultural festival arrives, and Rikako becomes more distant from the other girls, many of whom openly dislike her. Taku notices Rikako defending herself when another student tries to assault her and he is impressed by how she handles the situation. She slaps him again, then runs away in tears. Seeing Rikako cry leads Yutaka to punch Taku for not standing up for her, calling him an idiot, and the three drift apart for the rest of the year as they begin attending different universities.
At a class reunion years later, Rikako does not attend. Yutaka explains that he punched Taku because he was angry that Taku hadn’t pursued Rikako, even though he believed she deserved better. They watch the sunset over the sea and reconnect in memory. After the reunion party, Taku learns Rikako was visiting Tokyo to meet someone who supposedly likes to sleep in bathtubs. Later, back in Tokyo, Taku glimpses Rikako on a train platform and runs toward her, only to find that Rikako waits for him instead of boarding the train.
