Koko is a very young and playful Melos Warrior who leads insurgents in what she calls an "armed theatrical group" fighting against monster-run society. Koko is smarter than Bocca and more mature as a warrior, with an adult's sense of humour that somewhat compensates for her tragic past. She might be categorized as a dorodere and masegaki. Her last name is the Italian word for lullaby, and her special attack is Four Card (a reference to four-of-a-kind, a very good hand in Poker.)