When the world is full of danger and one fears for their lives, they reach out for protection. For some, that protection comes from the girls of Tercio, a private security company which hires individuals with "special genealogy." Despite their appearance and personalities, the girls are competent bodyguards who specialize in a number of skills. While carrying out the duties of a Tercio bodyguard, the headstrong sword-wielder, Tsukasa Yakuouji, feels as if she's searching for something...