I feel like the writer is trying to show us in a somewhat subtle way that Jaekyung is not good but Heesung isn't all that better. I mean think about it,Heesung seems to blatantly ignore Dan's requests while they were and only stalled his check up,or the underhanded way he did get to have check ups. Or how he's trying to buy the love of someone who clearly isn't interested. I mean,just look at the way he's acting with casual stuff. Not to mention hiding his true intentions.
Now I'm not trying to paint Jaekyung in a good light either, goodness gracious no,but I do feel like he's better in a sense that he isn't being sneaky about his intentions. He clearly states why he does the things he does with no sugar coating or sneaking around the subject,and though it really isn't much,he does sometimes take his feelings into consideration, again for purely selfish reasons,but he does it nonetheless,even when he really doesn't need to.
Again I'm not saying that Jaekyung is good, I'm just saying that he seems...better than Heesung,going but subtle clues. I could just be overthinking this one though,but I really couldn't get this thought out of my head