Oh Je Ro (Choi Min Ho) is a musical genius who had always dreamt of learning the piano, but had to work in a piano factory as tuner instead of going to school, in order to support his sick father. He had despaired of ever being given a chance to learn and thought the name his father gave him sounded like "Oh, Zero", signifying his lack of hope in the future. This changes when he meets an elementary school piano teacher, Yun In Sa (Han Ji Hye), who tries to spark his musical ambition so that he doesn't end up like her, sad and hopeless. They fall in love, but Yun In Sa is not so sure about the future potential of this relationship, which however is a catalyst for their lives. What will happen to the couple?