Well... I randomly came across this music video.
And I have also been listening to some N.Flying songs recently after seeing one of the members in a web drama.
The description says:
N.Flying Special Digital Single 'STARLIGHT' is leader Lee Seung Hyub’s own song with beautiful and sentimental lyrics which was written while looking at his grandmother's heart for deceased grandfather.One comment says:
This song is written by Seunghyub and its about his grandparents, whom his grandfather passed away and he noticed that his grandmother had been using his grandfather's photo as a profile pic on social media with a caption meaning "forever friend", so he was inspired to write this song... so the illustration in this mv is basically his grandparents, which his grandfather is becoming a child again (its also in the lyrics) and slowly losing his memories (represented as balloons) and the last memory he kept before he left was his grandmother (which was the balloon he drew on)