Shuji and Chise are two high-school students who have just started going out. One day, while visiting Sapporo, Shuji is caught in an air rate by an unknown foreign power. As Shuji runs through the city streets, avoiding falling bombs, a mysterious weapon appears and single-handedly wipes out the swarm of bombers. The weapon? His girlfriend, Chise… What do you do when your girlfriend becomes the ultimate weapon?