Nagisa Aoi is a new transfer student into one of the three prestigious all-girls Catholic high schools on Astraea Hill: a school called St. Miator (the other two are St. Spica and St. Lelim (known in the anime as Le Rim, for some reason). While getting totally lost on her first day, she stumbles into a clearing with a tree, and also into a girl with long silver hair. Nagisa is immediately smitten with the girl, Shizuma Hanazono, otherwise known as the Etoile of the three schools (the most idolized girl). Shizuma, after picking up a figurine dropped by Nagisa, kisses her on the forehead, leading to Nagisa fainting. After waking up in the school's infirmary, Nagisa then meets her new roommate, Tamao Suzumi. Things, however, will be getting a lot more complicated for the new student than just that.

Schoolgirls discover that they have been given the ability to materialize weapons and control robotic beasts called "Children" to stop an evil organization from their plans of domination.

Satou Matsuzaka, a girl who has never loved anyone before, falls in love with a girl named Shio Koube. The two girls are drawn to each other, and begin a happy life together. Satou won't let anyone endanger their new life, and would do anything for love, even if it means threatening, confining, or killing someone.

Kämpfer 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 main series covers 12 volumes, while the remaining three are short story collections. A manga adaptation by Yu Tachibana started serialization in the April 2008 issue of Monthly Comic Alive. A 12-episode anime adaptation aired in Japan between October and December 2009 on TBS, concluded in spring 2011 with Kämpfer für die Liebe. The series has extensive use of the German language.

Haruka Takayama and Yū Sonoda were inseparable during middle school, but upon entering high school, they end up being seated on opposite sides of the classroom. Having to spend time with more friends, the two decide to make their relationship special by kissing each other in secret.