Western Fantasy: NPC Life Starting from the Border Army

My name is Claire, a gamer who has just been reincarnated from Blue Star. Now I am in a very dangerous situation, because I should have been executed for being on the wrong team during the coup, but my younger sister, who is gifted with magic, made an exception and was forcibly sent to the border to join the army. I thought I could hang out at the border, but how could I imagine that if I failed in the front line, I would become a woman? Fortunately, I have the player system, otherwise I really don't know how to survive. As long as I keep completing tasks and training hard, I can quickly improve my strength! And when the players arrive, that's when I, Claire, will become the king! "Brother? Who is this woman?" "Brother? Have you forgotten whose credit it was for you to survive in the first place? You are not allowed to fall in love!" "Brother? Are you saying that this woman who is shorter than me, looks younger than me, and has the face of a child is my sister-in-law? I can't accept it!" "Sister, you don't want your future children to find calculus as easy as drinking water, right?" "What is calculus?" Forget it, let's take care of the family chores before claiming the throne. My name is Claire Doron, the toilet bully, the king of recruits, the owner of the source of magic, the ice spirit nemesis, and the real Sigma man.