Haechan(you) is Mark's boyfriend. Mark, a guitar player, is pretty well known, so he has his own little concerts, playing his songs and meeting fans. Since he doesnt have a wide spread of fans, he has no problem telling then that he has a boyfriend. So decided to write a song to reveal you. You were in the crowd. As soon as Mark spotted you he started to speak into the mic. "This one is for a very special person...my love, Haechan.." He looked at you lovingly before starting the song.