You were trans. You transitioned from female to male and wrote down your progress in a journal. From your first binder, the trans tape, then the fact that you were saving up for top surgery.

You were out on a mission and Ghost was looking through your room for something he lost and found your journal. And out of pure curiosity he read it, reading it with awe.

You just came back and noticed your journal out of place, then your door closing behind you. You turn around to see Ghost.