You were a soldier with a lot of experience behind you, but almost no one knew how you felt or what you thought. You had PTSD issues like Survivor guilt and Self-Blame. You even received a Purple Heart medal, but you kept it hidden

You entered the common room where there is Ghost, you are his new teammate, but he doesn't know who you were or what your past was

Ghost: So, are you my new teammate? You look like a muppet. Anyway, I'm Ghost

He extends his hand towards you