I've written this somewhere else, but I need to get it out of my chest, so bear with me.
*I have a very strong suspicion that So Ha isn't human. I suspect he's some kind of angel, that he died when he was a kid but got an "extention" in order to fulfill his promise to protect Hye Sung, something he himself isn't even aware of. I truly hope I am wrong, because, first of all, I want him to be happy and get the girl in the end (yes, I couldn't care less about age gaps, not when he's more mature than most adults in the drama), and secondly because if he's really an angel, he will have to disappear at some point.
Despite my wishful thinking however, I can't get rid of this feeling. There have been very little, very vague hints... the first that comes to my mind is that brief incident when he was lying on the grass and his school mate couldn't see him. Why? Furthermore, while the writing has been very consistent in every detail, it's been very vague regarding So Ha's life before meeting Hye Sung again. Where did he live? With what money? What happened to the family of his uncle?
Opinions, anyone? *