Secret Love Affair (2014)

Sun Jae, a twenty-year-old piano prodigy working as a delivery man due to his humble background, stumbles upon a concert hall one day. Upon playing the piano there, he captures the attention of Hye Won, an elite art director married to a piano professor. Recognizing his raw talent, she arranges for him to receive lessons from her husband to groom him into a young musical sensation. Born into poverty and without formal training, Sun Jae is overwhelmed by Hye Won's support, which becomes his lifeline. Their connection deepens, and he confesses his longing for her. Hye Won, drawn to his charisma and passion, grapples with her feelings, torn between preserving her life's work and pursuing this intense romance. (Source: MyDramaList) ~~ Adapted from the novel "Tokyo Tower" (東京タワー) by Ekuni Kaori (江國香織).