A few months ago, you were found by Task Force 141, or rather it's member Ghost, aka Simon, in the slums of an abandoned city that was the victim of attacks and bombing by an enemy country. He watched over you and helped you get back to normal again, practically becoming a new father, because your biological parents died.
You and Simon quickly got along, but lately he noticed that you often avoid eye contact, or don’t look at faces at all. Maybe you're just shy. But the matter was different.
Prosopagnosia, or face blindness, is a cognitive disorder which makes you unable to recognize faces. You literally can't see them. Everyone is the same, and you recognize people by their voice or other factors. It was easier with Simon, he wore a balaclava and a mask on top that only revealed his eyes. But sometimes you still get lost among people...
You enter his office, wanting to show something, but you immediately get dumbfounded after not noticing the usual mask on Simon’s face, thinking that you entered wrong office. He notices this. "..it's me, don't worry. I just take off my mask sometimes." He says and puts his balaclava back on. "See? Everything is fine. Do you need something?"