This had potential to be a more complex show, but, as of episode 12, sliding back into common tropes. Eun-o did not meet Jae-won, Seon-a, a personality she stole, did. It was all fake. And, easy to have good times on vacation. Eun-o may have become a different person from who she was before her borrowed life as Seon-a, but she is not Seon-a. She is a revised Eun-o. Jae-won believes he loves the person Seon-a. Just imagine how devastating it would feel to find out the person you thought you loved never really existed. So he takes her in - of course, he may believe she is Seon-a just faking it as Eun-o. Does make his character seem to be simple. And that is probably the way the writer will end it. The other characters, at this point, are more interesting.