Eumak Cheonjae-reul Wihayeo

Kang Hyeon, who was ashamed of his poor family, cut off ties with those around him and studied desperately to achieve success, but eventually he realized that his ideals were wrong. To make matters worse, Hyeon, who has cancer, gets run over while trying to save someone who fell on the subway tracks, and returns to the past while listening to the melody of a symphony. Hyeon, who was determined not to live the same life as before, realizes that he has tremendous musical talent... (Source: Naver, translated)