2) He treats his girlfriend well
Nakwon might have that gf for status quo, but he does treat her fairly well. He took her out on a date, told her she was the most beautiful, even thought about her when he slept with Mokhwa (saying he shouldn't desire a man because he had a gf). I don't know about loyalty, but at least that meant that his gf was the best girl he could find who fulfilled all his requirements. He could have just not invited her to that one party and gone alone (because how should she know?) but he did invite her. We could argument that he did that only for the eyes of others but if she was really annoying then he would never.
3) Nakwon was in a band and had long hair
That info was so random and so minimal that people might have forgotten it but it meant that the career-climbing Nakwon had surprisingly a different life style that imagined. I imagined a class president, grade notes, tidy clothes and all that. But he also had a care-free past which adds to his personality and is refreshing.
4) Nakwon didn't like Mokhwa randomly one day.
Since chapter 2, he realized how he kept touching him, went to the shop to eat, slept with him twice and blushed during the 2nd time. He got mad when Mokhwa didn't know his name during that one dinner (like my existence is that insignificant to you??), helped hin at the shop and got jealous at the women who helped Mokhwa in prison. He was into him since chapter 1 but he just didn't want to accept it.