Youichi Nishijima

Kenzou Tenma, a Japanese brain surgeon in Germany, finds his life in utter turmoil after getting involved with a psychopath that was once a former patient.

Kaiji Itou is a good-for-nothing loiterer who spends his days drinking beer and stealing hubcaps—that is, until he ends up being tricked by his former co-worker. Unable to suddenly repay his friend's huge debt all by himself, Kaiji is offered a shady deal to participate in an illegal underground gamble on a cruise ship. This turns out to be nothing more than the beginning of his new life of hell—thrown headlong into a life-threatening roller coaster of mind games, cheating, and deceit.

The story follows a team of pirate mercenaries known as the Lagoon Company, that smuggles goods in and around the seas of Southeast Asia in the early to mid 1990s. Their base of operations is located in the fictional harbor city of Roanapur in southeast Thailand near the border of Cambodia.

When a shapeshifting demon with a thirst for human flesh, known as "youma," arrives in Raki's village, a lone woman with silver eyes walks into town with only a sword upon her back. She is a "Claymore," a being manufactured as half-human and half-youma, for the express purpose of exterminating these monsters. After Raki's family is killed, the Claymore saves his life, but he is subsequently banished from his home. With nowhere else to go, Raki finds the Claymore, known as Clare, and decides to follow her on her journeys. As the pair travel from town to town, defeating youma along the way, more about Clare's organization and her fellow warriors comes to light. With every town cleansed and every demon destroyed, they come closer to the youma on which Clare has sought vengeance ever since she chose to become a Claymore.

In an alternative feudal Japan, a strange disease that only affects males caused a massive population reduction, leaving females to fill the vacant jobs, therefore changing the social structure. Now, 80 years after the initial outbreak with a 1:4 male:female ratio, Japan is a completely matriarchal society. Females hold all important political positions, and males are their consorts. Only the most powerful female—head of Tokugawa shogunate—may keep a harem of handsome and unproductive males, known as "Ōoku".