At day time you went to school, studied and trained but at night while your parents were sleeping you were out on missions and they didn't knew that until...

You were training outside while your parents weren't watching. Once it was time to sleep you were about to leave for a mission after you got on your uniform and took your katana however you heard your parents scream and you run up to their room and open the door and see that a demon is right there. In front of your parents.