October is one of the triplet androids October, November, and December, the youngest-looking members of the Twelve Sisters assassin group serving Madame Marciano in the Criminal Guild. As third-generation androids, the triplets share identical design and function, appearing approximately eight years old. They favor physical force over firearms in combat, throwing objects or employing brute strength during engagements, distinguishing them from older sisters who typically use handguns or explosives.

October and her triplet sisters exhibit childlike behavior on missions, treating destruction as play. They show no concern for collateral damage, such as leveling buildings to reach targets. Their emotional responses align with other androids in the group, displaying programmed loyalty to Marciano, whom they address as "Mother." They operate under her commands without question, though their actions lack malice due to perceived innocence and limited comprehension of consequences.

Like all Twelve Sisters, October communicates via secure internal radio, possesses enhanced strength and durability, and experiences sensations like taste. She wears neo-Victorian maid-style clothing consistent with her sisters, featuring black, white, and red accents suited to her youthful appearance. Her narrative role remains confined to group actions alongside November and December, with no individual character development or distinct backstory explored.

The triplets' final fate is not explicitly detailed, though the Twelve Sisters' overall story concludes with Marciano's defeat and the survival of some members. October participates in all group combat sequences but receives no personalized resolution or standalone focus beyond her collective role with the triplets.