Fifteen years after magic and beings from another dimension entered the world, seven nations have sealed contracts with those beings, the Divas, and built academies that train swordsmen and summoners on separate tracks. Kazuki Hayashizaki, raised to the sword, is stunned to become the first male ever chosen by a Diva, which lands him in an all-female summoner class. The loudest objection comes from his own sister Kanae, the academy's finest swordsman, and Kazuki starts at the bottom of the Magic Division with everything to prove.