The series is set on a fictional medieval island where humans are plagued by Yoma (妖魔), humanoid shape-shifters that feed on humans. A mysterious group, known as The Organization, creates human-Yoma hybrids to kill Yoma for a fee. These female warriors wear armored uniforms. The public refer to them as “Claymores,” alluding to their Claymore swords, or “Silver-eyed Witches,” due to their silver eyes.
Yoma and Claymore warriors alike are powered by a demonic energy, Yoki, which allows shape-shifting and extreme strength. When warriors use too much Yoki, they “awaken,” becoming a super-Yoma called an Awakened Being. The act of awakening is likened to the feeling of sexual climax, so while both male and female warriors existed in the past only the women proved to be successful warriors and so the creation of male Claymores stopped altogether
The island world is divided into 47 districts, with one warrior assigned to each. Claymore warriors No. 1 through 47 are ranked on their baseline Yoki potential, strength, agility, intelligence, sensing and leadership. A warrior’s rank rises and falls according to the warrior’s strength in relation to other warriors. It is unclear whether the warriors strength comes from training/experience or if the potential lies within the warriors themselves