Kamine Shuuta is a person who can see a person's heart (literally) whether it's angry, wounded, broken, guarded, troubled etc... and because of this he's at his wits end, because he can't do anything about it.
Tokisaka Hibiki is a saxophonist in the music club. Shuuta first listens to his saxophone on the terrace and wanted to ask something but Shuuta tells him to come to his performance later in the ongoing school festival. After seeing Hibiki's performance, he see the notes of music as hands which can heal the wounded, tend the broken, break the shielded hearts: in other words "seize the soul" of a person.
After the performance Shuuta asks Hibiki if there isn't a person to whom your sound doesn't reach. Shuuta says although Hibiki's sounds can seize hearts of others and move them, his own heart is guarded and is unmoved and troubled. Hibiki then takes Shuuta to his childhood friend Moko (Takizawa Momoko) who loved singing but somehow became mute. Shuuta sees her as a sea of depression and despair. Thus begins their journey to heal people's hearts with music.