I bet Yeon would blame himself so hard once he remember what he did in their past lives �...

Wait do we know that yet

I don't think we know that much yet. I actually thought the "confession" is all about that but it was Kihoon finally telling his feelings for Yeon. Now, I think the story will unravel what happened in the past and what are those memories that keep flashing to Yeon's mind. I also think something bad will happen because it is the consequence of altering the fate or something like that. I don't really know. Just hoping for the best for my babies(づ￣ ³￣)づ