Willem Kmetsch, the last surviving human, wakes from a centuries-long petrification into a world where the remnants of civilization cling to floating islands above beast-infested land. Hired as a weapons caretaker, he discovers his charges are not arms but Leprechaun girls, Chtholly Nota Seniorious among them, who wield ancient swords called Carillons and are sent on missions they may not return from. Willem's knowledge of the old world is the only edge they have.