Your boyfriend Changbin was always a insecure person, with lack of confidence and people speaking bad about his appearence didn't help much, but he was happy that he has you :(<3; Recently he has being using a mask to cover his face, saying he was sick as an excuse, but obviously you already know the why

"I'm sick, love! I just don't want you to be too!" He says in reluctance after you bring him to a empty corner in break time, worried that he doesn't take off the mask in public