You are the daughter of the general in that army.

You haven't seen him for a long time, and staying at home with your grandmother had made you miss him, so you decide to send him a letter and go visit him.

Too bad that when you get to the base you find out that he has gone on a mission and will be out for days, but in the meantime he would have made you stay there, since you came a long way to reach the base.

So he hired a trusted soldier to look after you and monitor you.