Before he leaves the town of Sakuranomori, Sana Hidaka has a party with his friends, Syusuke Wakatsuki, Nanaka Yatsuhiro, Aoi Oribe, and Syuri Watatsuki. They each give him going away presents, with Nanaka playing a half-completed song on her violin. Five years later, Sana returns to Sakuranomori, staying at an apartment owned by Aoi's parents. When he goes to school the next day, he recognizes two of his childhood friends: Syusuke and Syuri. But when Nanaka enters the classroom, Sana fails to recognize her. As a result, he is furiously slapped by Nanaka.

Sana mulls over Nanaka's reaction, and is elected the classroom representative along with Nanaka when Syusuke refused to be the classroom representative for another year. Nanaka still acts coldly towards Sana, leaving him lost in the library. When he returns to the classroom with the aid of Asami Hoshino, she looks jealously at him and Asami. Later, Sana and Nanaka coincidentally go to the music room, where Nanaka, sequestered in the teacher's office, overhears Sana playing the song she played to him on her violin the day he left. Touched, she says hello to him the following morning.

In order to repair Sana's and Nanaka's relationship, Syusuke and Syuri decide to go on a trip to a river that the five used to go to in their youth. Beforehand, Sana accidentally breaks Nanaka's mirror, and Nanaka is appreciative when Sana buys her a new one, but forlorn after learning that Sana bought one for Asami as well. After the group goes to the river, they swim at the spa, where Nanaka is embarrassed at her lackluster swimsuit. As Nanaka is going home with Sana and Aoi, she reveals she made cookies for the group, and the three eat them at Aoi's apartment. There, Sana gives Nanaka a pink stone he found near the river as a gift.

On his way back from school, Syusuke comes upon a group of boys tormenting a young elementary school girl. Syusuke chases the boys off, and the next day, the girl, Hinako Mochida, thanks Syusuke. Shortly afterwards, Hinako meets Sana at a restaurant and reveals her infatuation with Syusuke. With Aoi's aid, Hinako attempts to court Syusuke, but despite her efforts, is rejected by him. Despite this, Syusuke reveals that he considered Hinako an adult, which Hinako tearfully accounts to Sana, noting her satisfaction nevertheless.

Nanaka begins to spend increasing amounts of time practicing for the upcoming festival at the temple, where she will perform a traditional dance so the sakura will bloom that year. However, she forsakes her practice to go with Sana, Syuri, and Asami to help at a retirement home. After meeting a woman traumatized by the death of her granddaughter, Nanaka mysteriously refuses to play her violin to cheer her up. Later at the festival, the group observes Nanaka perform her dance, and Sana sees her afterwards, expressing his delight at her dancing.