Nanaka Shirakawa is a student at the Kazami affiliated junior high school, attending class 3-2, and is widely regarded as the school idol. She is known for her sweet and kind disposition, her intelligence, and her musical talent, particularly her singing voice, though she is initially reluctant to perform in front of an audience. Nanaka serves as the lead vocalist of a band she forms with her best friend Koko Tsukishima on bass and fellow student Wataru Itabashi on drums; later the protagonist Yoshiyuki Sakurai joins them on guitar. Like her grandmother Kotori Shirakawa before her, Nanaka possesses the ability to read the minds of others, but only when she is physically touching them. This power was granted by the island's magical sakura tree in response to a wish she made during a period of bullying she experienced in her adolescence.

Nanaka's role in the story is that of a supportive friend and a romantic interest. She is deeply close to Koko, with whom she shares membership in the music club and a tendency to struggle with expressing her own feelings and concerns. Her motivations are initially centered on her friendships and her love of music, but she gradually develops romantic feelings for Yoshiyuki after he defends her against girls who were insulting her and later rescues her when she becomes trapped on the school rooftop during a storm. This growing affection creates an emotional conflict within the group, as she is aware that Koko also has feelings for Yoshiyuki. Over the course of the series, Nanaka shows development by becoming more willing to open up about her emotions and to step forward as a performer, culminating in her singing at a school event to support a friend. Her mindful reading ability, while not heavily used in combat or plot-driving scenarios, serves as a narrative tool that highlights her empathy and the loneliness she once felt, and it informs her interactions with those around her.