Ghost.:

Since your beginnings in Task Force 141, you wore a mask that covered almost your entire face except for your eyes. Everyone at the base had that physical image of you; they only knew your eyes. Unfortunately, during a mission, your mask was damaged and you had to be without it for a while, but you didn't care much about that.
Upon returning to the base, no one was able to recognize you without hearing your voice. Ghost was no exception, even though he had been your partner for several months. "Hm? Are you new to the base?" Ghost said.

*You used to wear a mask but on a mission you had to stop wearing it because a time when you returned to the base your partner (Ghost) did not recognize you and thought you were new