My small theory is this: he has monolid squinty eyes.
Since this is lookism and all, everybody really values being beautiful, and having monolids are not considered beautiful in Korea. Not to mention he came to Seoul to become a singer, that's even more of a big deal
I just think that he has such a low self-esteem.
Actually, that would make sense.
Wait-Jae Yeol came to Korea to become a singer? Where does it say? I never knew that!
I think Rosa misunderstood and was talkin bout the dude with the sunglasses
I have 3 small theories behind the mysteries of why Jae Yeol's eyes are covered.
1. Could the reason we don't see Jae Yeol's eyes have something to do with the fact that he has a condition similar to Joon Goo (the body guard of Crystal) or Jin Ho Bin where he becomes someone different/crazy when his eyes are uncovered? If so, that would explain why Jae Yeol always has hair covering his face. He could have once been a delinquent or someone scary prior to high school. In the past, he used to smoke cigs and beat people up (on account of protecting Hyung Suk) which gives him an impressin of a lowkey deviant.
2. He's not actually full Korean but Russian. (Well, half, anyway). Here's one clue: his fighting stance.
It is known that he uses a Russian-style martial arts technique (Systema) which even Logan remarked, is kind of odd and unexpected. It could just mean his unusual style is meant to highlight his overall mysterious aura like Batman, but where would he have learned the technique since it is probably not taught in Korea as readily as Judo, Tai Chi, Taewkondo, or boxing, which are more popular?
My best guess would be that it was taught to him by someone who is RUSSIAN. Which brings me to my next point:
Jae Yeol strikes me as someone who is shy and not used to attention probably because his upbringing wasn't all that happy or nurture-filled. His father could have been a rich businessman who had an affair with a Russian woman, gotten her pregnant, had Jae Yeol who looks slightly different (maybe his eyes) then could have been raised in Russia while facing prejudices from his stepmom (not biological) and her Korean family for having non-Asian eyes, reminding them of the woman who had a fling with her husband. In short, a child born out of wedlock (bastard child). Jae Yeol must have been picked on/bullied at a Russian school for looking more Korean than Russian harkening him to be a loner. The bullying might have worsened to the point where which drove him to want to fight back. Some Russian martial arts master of Systema might have showed compassion by teaching him to defend himself.
After mastering Systema, one day he would fight back against his terrible bullies and injure them to the point of hospitalization. His "famiy", not hearing teh details (or perhaps not wanting to) maybe see him as a troublemaker. Not knowing the full reason either, his father would then move him maybe thinking he'd be more at home and away from his trouble, to a new school (in Korea) where he would later join Jae Won High and display quiet deviant behavior such as smoking or dressing a certain way (maybe because now he doesn't care anymore). I mean, think about it, there was a chapter where Jae Bae was in the bathtub talking on the phone and he was strongly advised not to go home to meet his family because "you and everybody will be uncomfortable" was what was told
http://www.mangago.zone/read-manga/lookism/bt/c585b81d421db479/Ch47/pg-10/
Then along comes the kind compassionate Park Hyung Suk, whom he falls in love with...