I came to comment after reding 14 chapters, this reminds me of that Bl love mechanics where the guy(V) kept on hitting/sleeping with another guy (mark) although he himself had a girlfriend (i forgot the name, let's call her x), turns out the girlfriend was also cheating on the guy. Quite a similar vibe I am getting here! Jaehee keeps on saying he loves yeonwoo and can't break up but sleeps with the Prof. Vee did same, Initially he didn't wanna break up or wouldn't break up with the girl but slept with mark and would get jealous when mark is with another person!
On another note, i hate cheating trop! Sad to see so many manhwa and shows out there showing/glorifying It, although it happens in real world.
. This cockroach is still alive. He deserves the name cockroach. ヾ(☆▽☆)