September, a combat android forged among Marciano’s Twelve Sisters, serves dual roles as assassin and surrogate daughter to the childless cyborg matriarch. Her creation embodies Marciano’s longing for familial connection, though September’s unwavering loyalty meets only detached indifference.

She mirrors a late-teen girl in appearance, standing 5’5” with brown hair framing straight-cut bangs and bright blue eyes. Her synthetic body lends unexpected heft beneath a traditional maid costume—a crisp white and black uniform accented with crimson trimmings, paired with white stockings and polished black shoes. Armed with an M14A1 rifle and fixed bayonet, she dominates both ranged and close combat, leveraging enhanced optics to land lethal precision shots—famously striking three consecutive headshots mid-parachute during the Sandvil prison assault.

Prone to reckless bravado, September charges into solo engagements, prioritizing battlefield theatrics over teamwork in her desperate bid for Marciano’s approval. This overconfidence seals her fate when she single-handedly storms the Coyote’s ship, overwhelmed by coordinated rocket barrages and explosives.

Trained in Jukenjutsu bayonet tactics and acrobatic Jujutsu throws, she deflects strikes with her rifle and sacrifices positional advantage for crippling counterattacks. Yet her tactical impatience and habit of dismissing adversaries’ capabilities lead to fatal errors.

Her story concludes abruptly in Episode Three, distinguishing her as the sole Sister permanently decommissioned in the series. April coldly relays her destruction to Marciano, who acknowledges the loss with a clipped diminutive—“Sep”—highlighting the group’s transactional bonds.