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.

After learning that her mother will not be home for her birthday, Hinako moves into Sana's apartment. Hinako's inexpertness in cooking and Sana's shock at her arrival contributes to the hectic situation, but Sana manages to get her comfortably situated into the room. She was not able to sleep without her Yeti giant soft toy and asks Sana to be her Yeti and let her hug him. Sana eventually learns that the day was Hinako's birthday, and the following day, takes her around town with Syusuke. Once they return to Sana's apartment, Nanaka, Aoi, and Syuri have prepared a birthday party for Hinako. After Hinako leaves the party, she thanks Sana for the only birthday party she has ever had with a kiss on the cheek before running home.

Sana visits Asami in the hospital, where Asami reveals that she was the one who sent the anonymous letter claiming that Syuri and Syusuke were in a love hotel. She admits that ever since Syuri rejected her for expressing her feelings towards Syuri, Asami has constantly hated her. When Syuri and Syusuke arrive to visit Asami, she acts normally, although she asks Syuri to converse privately with her. Syuri later runs out of the hospital in tears. The following day, Syuri and Syusuke are absent from school, and Sana realizes that they are running away to avoid being separated. He desperately runs after their train, and reminiscent of Syusuke when Sana left town, Sana yells that they will always be friends, and Syusuke and Syuri erupt in tears.