The ending of episode 12. It was so sweet. When Mudeok says to Uk that he shouldn't come near her, but he still gives her a hug, not caring about possible consequences. Uggh, my heart melted in that moment. Also, when Uk takes the leap from the tall island into the unknown for Mudeok.
And the mirror scene was very sweet, Uk was determined to find her even if he was to be stuck in the Jin's special room forever.
I also found the scene funny where Uk was telling Mudeok about the special ability the jade stones have and she believed him, and then the smile that Uk gave. He's like, hehe, i cant wait until i get that stone back for you.