Chaeyoung learnt the hard way that even 5 innocent letters, could change your whole life. For the worst or the better.   

"Children make up the best songs, anyway. Better than grown-ups. Kids are always working on songs and throwing them away, like little origami things or paper airplanes. They don't care if they lose it ; they'll just make another one." - Tom Waits  Michaeng soulmate AU.