Naui Boyfriend

Sin-Bi, a piano prodigy, has been harmonizing with Tae-Ui, a genius boy soprano, for a long time. One day, Tae-Ui suddenly leaves to study abroad, and Sin-Bi, a piano prodigy who returns to being an ordinary student, begins a competition challenge after a dramatic reunion of two high school students five years later.

(Source: Naver, translated)