Thanks to cipp and halmoni if you're still reading this.
I really like the "showdown" between Sung-Pyo and Seol-a. At first my reaction was annoyance as well when he mentioned Seol-a's nails (big guys dont do that lol). But looking at it in a less biased perspective, Sung-Pyo's still a nice guy who has strong lingering feelings for No-rae. When you're acting out of your feelings, it's usually irrational. He was just trying to find any possible excuse he could think of, to stay longer with No-rae. For that moment alone he became a douchebag towards Seol-a. And I loved it when Seol-a didn't back down. It gave a clear contrast between Sung-Pyo and Seol-a's personalities, and showed us whose characteristics would match with No-rae. Seol-a is now more decisive and not afraid to mark her territory. It's quite funny she doesn't care to show her courtesy for him in front of Hye-Kyeyung.
Maybe it's time for No-rae's POV though.