Natsuru Senö wakes up to discover one morning that he has transformed into a woman, upon which a stuffed animal tiger, Disemboweled Tiger, who introduces itself as a messenger, tells him that he has become a Kämpfer, which must do battle with other Kampfer; since Kampfer must be female, Natsuru transforms into a female version of himself. The next morning he is attacked by another Kampfer named Akane Mishima wielding a sidearm. Natsuru protects his friend Kaede Sakura from Akane's attack, before saving Akane from a falling lamppost...