Kämpfer

Kämpfer (TBS, 2009) is a Japanese romantic comedy anime series based on the light novel series by Toshihiko Tsukiji and illustrated by Senmu from Nomad animation studio. Natsuru is selected to be a Kampfer, a mystical fighter who has to fight other Kampfers, but the catch is that all Kampfers are female, and Natsuru is male... at least he was!