December is one of three identical combat android triplets—October, November, and December—forming part of Madame Marciano’s Twelve Sisters, a cadre of robotic daughters serving as assassins. Childlike and mischievous, the trio approaches missions as playful games, peppering operations with whimsical demands for snacks or chants for canned peaches despite lacking biological needs. Their appearance mirrors young children aged five to eight, with blond ponytails, wide brown eyes, and Victorian-style sailor outfits. Each carries a colored teddy bear backpack (green, brown, or pink) to distinguish them, concealing weaponry like December’s H&K MP5K, though she favors hurling armored vehicles or shattering barriers with raw, superhuman strength.

Inseparable in combat and daily routines, they attack with synchronized ferocity, overwhelming targets through sheer force or firepower. Their bond borders on codependency, risking volatile retaliation if one is harmed. Programmed to mimic human habits like eating or napping, December often dozes mid-mission. Loyalty to Marciano intertwines with a childish craving for praise, their obedience framed by innocent eagerness. No expanded backstory exists beyond their role as efficient, emotionally simplistic tools within Marciano’s operations, their narrative anchored to collective function and interactions among siblings.