Responses
My theory is that he unconsciously knew (because the author said that Sungyeon had many girlfriends before meeting Hosik) and that he only regained his memories when he saw Hosik under the cherry blossom tree that was similar to when Hosik stood under the cherry blossom tree in their past life
Or even when Hosik was in a coma after giving birth to his baby girl, he could have gotten his memories back, but I'm not too sure......
That's my take on it all.
Did seoyon know about their past life and thats why he such a control freak and wont ñeave him alone? Dont get me wrong i like the story but damn he wouldnt have ever let hosik go from the start