He acquitted himself well in these episodes so I must give him credit. (cough cough I’m not fangirling.)
1. This is a swoon-worthy moment for SeJoo.
credit: secondleadclub
He shielded her and took that blow for her without flinching or grandstanding afterwards.
2. He tried to find a start-up business that utilizes his networking ability AND his shady (lol) tactics, Actually, his proposal here is quite… surprising.
“According to matchmaking agencies, 55% of women and 42% of men want to cheat. This is reality. If you include potential cheaters who declined to answer truthfully, this is a blue ocean.”
credit: choi-sooji
When SJoo said Blue Ocean, he was referring to a business theory that says a company is better off separating itself from the rest of its competitors (imagine a boat sailing away from a fleet) and finding a new market in blue oceans, or “uncontested market space.” For a high school graduate, SJ was keeping abreast of new business concepts and strategies. 😉
3. He honored the Bro Code and waited his turn. He didn’t “steal” SooJi from his buddy.
4. He bore pain well. He may be beaten up at home, but he was whipped by SooJi everywhere else. AND he knew it.
Cue the sound of puppy yelping after being scolded. 
credit: ipeach
I can’t still forget this. Please, Sejoo, run away from this witch. Can you imagine being greeted by her like this when you make a mistake? What a hell-acious marriage.
credit: krystal
5. He cared for his mom when nobody else did.
I admired the friend of TH for staying home with her sick mom, but this guy has been visiting the hospital regularly anonymously. Plus, he gets bonus points for actually conversing with his mom when she’s comatose. The only way I’d deduct points from him is, in a cruel plot twist, he’d been the one to cause this to his mom.
6. He didn’t take advantage of the situation and force a kiss on her just to teach her a lesson.
credit: mochiminii
lol. He’s not entirely black like Valmont either. I hope he doesn’t end up like one of the characters in the sad drama movies he likes to watch.
credit: hyuitians
beautiful. He’s been pretty nice these last few episodes. I liked the comments you exchanged with Table122000 on the-great-seducer-on-sejoo about the difference in episodes 13-16. I think one of the differences between SeJoo and SooJi is that he can be super nice and caring with the people he actually loves. He’ll think about them and their needs first and not about what he wants from them like SooJi does with SH and him.
What if SooJi challenges him to prove his loyalty to her by going up against SH? I’ll bring out the popcorn if ever this happens. It’ll be fun to watch the fangirls’ heads overheat and explode when they have to choose sides: SeJoo or ShiHyun. 😀
Nice post. Your post really illustrated for me what a layered character Se Joo is. He is both good and bad. As @oli says, if you are one of Se Joo’s “people” he can be quite caring and supportive. With Soo Ji, we see his unconditional love and support in action. He accepts her totally, selfish ways and all. He’s also quite loving with his Mom and a good friend to Shi Hyun. However, if you are not part of his inner circle, Se Joo can be cold, calculating, manipulative, and oftentimes ruthless to get what he wants. He plays the clown, but underneath he is very smart and uses the fact most people underestimate him to his advantage. I agree with @packmule3 that Soo Ji will challenge him to take sides regarding her or Shi Hyun. It will be sad to watch because he cares for ShiHyun deeply as a friend/brother, so I’m sure he will be quite conflicted. Ultimately, he’ll choose Soo Ji, but not without heartbreak.