Aoba Tsumugi was a second year high school student when she heard the voice of a male student during a morning assembly and was attracted to it. The male student was Sakura Sou, who was reading an essay on stage. In the third grade, Tsumugi and Sou were in the same class and slowly started dating. Their relationship deepened through their shared hobbies in music but Sou suddenly left Tsumugi and disappeared one day after their graduation. Eight years have passed since then and Tsumugi has started a new life until she happened to see Sou in the crowd. She later finds out that Sou is suffering from sensorineural hearing loss, a condition that gradually makes people deaf and Sou has almost lost his hearing. This is a sad but warm love story between two who meet again in a world without sound.