It's really an irony that whenever Kangjoon feels sad,has puffy eyes due to crying,Yeon Seol thinks he is the reason but now that he knows Joon feels better recently,he can't help but think of someone else being the reason!
Is he selfish?yes,but I guess he's not too dumb to have insecurities!
Now I feel like the main story was actually a bunch of side stories!
Now that you said that