Favorite drama ost song of 2015

Been listening a little to youtube mixes of drama osts and I gotta say there is one that still sticks in my memory and I keep relistening to it and always feeling so awwwww after it :D Song + the drama itself was for me best pick of 2015 :D 

Also a little about the drama Healer, just little, better worth the watch :D Our main boy, under pen name Healer works as night courier, does what the job says as long as he can get the money for it so he can realize his dream plus is kinda loner because the works can get dangerous so he don't really make connections with people etc. Then we have our main girl who works as reporter and there is another reporter she respects but he is looking for his niece (one of the Healer's tasks) and our girl reporter is one of the possibilities. Later the male reporter asks Healer to protect her and so we get to see his kinda Clark Kent side as a clumsy, easily scared and shy boy who joins the reporter station she works at. All three later find their connection to one another. 

As for the favorite 2015 ost song from here, I'll add the link + has some scenes from the series :D

Also I agree with this list, many many good 2015 ones <3