Best episode by far!
Episode four accomplishes a lot making it one of the must-see episodes. I can't really say a lot without giving away the reveal but lets just say shit is a bout to go down. I feel like this will shift from a romantic comedy, to a pure revenge story on the people who have wronged the main protagonist. I was worried in the first episode that the love portion of the drama would be too cliche, but I was ever so wrong. I'm really looking forward to the next episode, seriously.
What also makes this episode great is the really good acting. I think this displays some of Ye Seul's best acting here. She has to pull in a lot of emotion and a lot of stress in this episode while also making it believable, and she succeeds in it for me. Sang Wook is good here. The villains are good at being villains. Sara's mother is great here too. The side story seems really promising as well. Overall, out of the four episodes that have come out, this is probably my favorite. The shift from a comedic romance to a dark revenge story is a great plot-twist in my opinion.