Kämpfer (けんぷファ, German for “Fighter”) is a Japanese light novel series by Toshihiko Tsukiji, with illustrations by Senmu. The series contains 15 volumes published by Media Factory under their MF Bunko J imprint between November 2006 and March 2010.
The plot revolves around Natsuru Senō, a normal high school boy with blue hair. One day he wakes up and found himself turned into a girl. A stuffed tiger “Harakiri Tora” comes to life and tells him that he has been chosen as one of the “Kämpfer”, a female fighter. The Kämpfer are destined to fight with other Kämpfer. The story starts when he is attacked by an unknown girl who happens to also be a Kämpfer.