There was a girl named Yuki in a certain building in a certain magical world. She was given the task of driving back intruders, and although she sometimes lost, she enjoyed her assigned task to the fullest. But when did she start? However, an intruder with great ability appeared, and she gradually became unable to win. She has been losing more and more recently, and the gold coins she receives as allowance are running out before she can spend them. In order to break out of this situation, Yuki decides to go into training to make herself stronger...