My interpretation is that people were looking out for sung Jiwoo back at the beginning even though he didn't know or ever realize it, that the association recruited that healer to try and keep him alive because he wouldn't quit. In the same manner now he's training his son on how to use his powers and if he learns how to master them he'll finally be unsealed. If his son gives up, then I'm sure the training would stop, but he knows his son is like him and won't stop no matter what. So in the same vein he has to help his son help himself without him knowing, as it would make him realize what he has before he's ready.
I see. So that first part is kinda like a flashback of Jinwoo's past. Now, I get it. Thanks. Also, am I the only one who's rooting on Jinwoo & Juhee?
Am i the only one who did not understand the last chapter???