Based on Tsukiji Toshihiko’s light novel series Kämpfer. Author Tsukiji Toshihiko is also the creator of Maburaho and the concept behind the “Sea Story” pachinko games. Senou Natsuru is your normal, everyday high school student. However, one morning he wakes up and finds himself turned into a beautiful girl over night. A stuffed tiger "Harakiri Tora" tells him then, that he has been chosen to be a Kämpfer (German for "fighter"), whose objective consists of fighting other Kämpfer with either guns, swords or magic. Natsuru has been granted great strength and fighting abilities on top of the power to use magic but finds out that only girls can be a Kämpfer. Left without another choice, he is forced to turn into a girl to fight other Kämpfer to survive.