Did you know that the lyrics for the 4th OST, ‘Dear Moon’, was written by IU herself?
Here is the song performed in her own lovely voice.
In one of her episodes for IU TV (7’18” onwards), she talked about her experience writing the lyrics and confirmed that to Ji An, the moon is Dong Hoon himself.
(Watch her full answer as it goes really in depth into her thought process and the meaning of ‘The Moon’ to both Ji An and her grandmother.)
My Ahjussi / My Mister Fan Site 