Natsuru Seno is your standard teenager that goes to an all-boy's school...except when he (through no control or will of his own) transforms into a Kämpfer, a female warrior tasked with taking down those like herself. Now he—or she—must entroll in the all-girl's sister school, but when a newspaper article calls her "The Yuri Girl of Seitetsu Campus," she now is forced with dodging love confessions and idol meet-and-greets alongside the bullets of an unknown Kämpfer looking to taking out the new idol of the school. Can Natsuru survive all this and still get those pictures he promised a friend?