The sisters turned Jang Uk's character into a Playboy in season 2.

Then Uk kisses her thinking of her with Jin Bu Yeon in ep 4, that is (a new love interest), since he didn't know it was Naksu yet.
It's just that he wasted no time "changing" women this season. Uk goes to the cliff where Naksu had met her death and says goodbye to her, and goes drinking to his room and that same night he already has Jin Bu Yeon lying in his bed!

He walks with her back and forth thinking of her as "Jin Bu Yeon" until ep 8. And they even kiss without the revelation! Worse yet he asks her to marry him and almost makes love to her thinking she is another woman!

In ep 9, he finds out who she is and RAPIDLY agrees to be with her, he didn't even think twice about it!!!