Wow, talk about shooting yourself in the foot. This chapter basically spells out that the feelings are mutual between Joonwoo and Hamin for the most part, but due to his inferiority complex, he's consciously denying his feelings by claiming he "doesn't know why he's so bothered by this". I say consciously because he does reason with himself that "these feelings are pointless". Joke's on him because he doesn't know that Hamin basically feels the same way or is almost at that point...
This kids, is why one should always properly try to convey their thoughts when communicating with others.
That aside, I now understand why he's so pissed at Jeong. He isn't mad about the fact that he was bullied by him in the past, he's mad because he thinks the girl he likes is interested in Jeong of all people. Basically, it's one of those "why are you always somehow at the heart of my suffering?" moments. I'm pretty sure if it was someone else, while he would have still been bothered, it wouldn't be at the level it is right now.
I was ready to call Joonwoo a hypocrite for forgiving Lila, but giving Taeyang and now Jeong shit for it. However, despite the fact that his anger here is misplaced, I can understand why he's mad and it isn't hypocrisy in this case.