Batako-san, also known as Butterko, serves as the primary assistant to Uncle Jam at his bakery. Her Japanese name translates to Butter Girl, reflecting her association with the bakery's daily operations. She is a consistently bright, optimistic, and caring individual who approaches her duties with diligence and a polite demeanor. Despite her hardworking nature, she is occasionally portrayed as being somewhat forgetful or careless, adding a gentle, relatable flaw to her character.

Batako-san was present at the moment of Anpanman's creation and, alongside Uncle Jam, helped raise him, forming a close familial bond that has strong maternal elements. Her primary role in the story is supportive, focused on the upkeep of the bakery and the maintenance of the hero Anpanman. She is skilled in baking, cleaning, laundry, and delivering goods. A critical part of her duties is restoring Anpanman's strength. When his head is damaged, dirtied, or weakened from feeding others, she provides a replacement head freshly baked by Uncle Jam, often throwing it to him during battles. She also possesses significant sewing skills, creating and mending the flying capes for Anpanman and other heroes, as damage to a cape results in the loss of flight. Demonstrating her resourcefulness, she once designed a special transparent helmet for Anpanman to protect his head from rain or during underwater missions.

Batako-san's key relationships are centered on the bakery. She shares a deep loyalty and familial care with Uncle Jam, though the specific origin of their partnership is not detailed. She has a particularly close bond with Cheese, the bakery dog. She was the one who named him, advocated for him to stay at the bakery, and frequently interprets his barking for others. Her interactions with other heroes like Shokupanman and Currypanman are amicable but less prominently explored in the narrative. An early narrative concept suggested a long-distance relationship with the character Omusubiman, though this idea was not pursued in later stories. While Batako-san appears human with rosy cheeks, black eyes, a small button nose, and spiky black hair often hidden under a chef's hat, the Anpanman universe features very few humans, leaving her exact classification ambiguous. An earlier concept for her backstory proposed that a young Anpanman discovered her as an infant in the woods, but this was discarded to establish her as older than Anpanman and a pre-existing member of the bakery. Across the various films and episodes of the franchise, Batako-san undergoes no significant character development or unique narrative arc, remaining a consistently dedicated, kind, and indispensable supporting figure focused on the well-being of the heroes and the operation of the bakery.