Rather than his face, it was his hair. She questioned him about it, and you can see that it looks choppy, my guess is that he was already experimenting with haircutting (or probably just didn't have the money for it?) and as a little kid, he did a bad job. His mom is clearly emotionally disturbed, I wouldn't be surprised if that was just an excuse to abuse him.
But as for the bully, I also thought that they might be related somehow. Ngl, at first I nearly got a heartattack, thinking it's the ML, but thankfully he doesn't have the second mole but it's really sus, that they have one in the same spot.

was scared seeing the bully's mole and then ukawa's mole the next pages... thank goodness it's a different person. BUT why do they have moles in the same exact position??? im pretty sure that's intentional. are they... twins??? or brothers at least? half-brothers? im just guessing the last one cause ukawa's mom seems to have hated his appearance(?). im probably reading too much into it but his dad probably cheated and had a kid with another woman and ukawa's mom hated his face for looking like his dad/dad's other son. lol im writing a whole fanfic!