Kanashiki Koiuta

From Strawberrie:

As a child, Joon-young was always teased because his mother owned a bar that served Americans. When he meets Hae-in, a blind girl, they become childhood sweethearts and he vows to always protect her. However, Hae-in and her mom take off one night, leaving Joon-young and his promise behind. Hae-in later meets Gun-woo, the rich son of a CEO. Among these three, a tragic love triangle begins to form...