Batako-san is a central character who works as the primary assistant to Uncle Jam in his bakery. Her name means Butter Girl, reflecting her connection to the bakery's ingredients. Physically, she is taller than Uncle Jam and has rosy cheeks, black eyes, a small round button nose, and spiky black hair that became shorter as the series progressed. Her typical outfit consists of blue overalls worn over a white vest, paired with a chef's hat that covers her bangs; when she removes the hat, her hair reveals a bowl cut.

Batako-san is defined by a kind, caring, and polite demeanor, and she is rarely seen arguing with others. She is bright, optimistic, and exceptionally hardworking, constantly engaging in tasks such as baking, cleaning the bakery, doing laundry, and delivering goods. She is also highly skilled in sewing, serving as a seamstress who frequently mends the torn capes of Anpanman and other heroes; without her repairs, these capes cannot be used for flight. Beyond baking and sewing, she is capable of crafting other items, such as dresses. A recurring personality trait is a tendency toward occasional forgetfulness.

Batako-san was present at Anpanman's birth, when a star of life flew into Uncle Jam's oven, and she helped raise him alongside Uncle Jam, forming a family unit. She serves as a motherly figure to Anpanman, providing essential care by helping to replace his head when it is damaged or depleted from feeding others and by stitching his cape when it is torn. She also designed a special transparent helmet for Anpanman to protect his head during rain or underwater missions. Her loyalty and dedication to Uncle Jam are profound, though their specific history before working together remains unknown. She shares a very close bond with Cheese, the small dog who lives at the bakery; she was the one who named him Cheese, advocated for keeping him, and often interprets his barking for others. The two are frequently seen delivering bread together, sometimes with Uncle Jam. She also maintains friendly relationships with other heroes such as Shokupanman and Currypanman, though these are less explored. Early concept art suggested a different backstory where she was found as an infant in the woods by a young Anpanman, but this was discarded, and she was instead established as being older than Anpanman. A long-distance relationship with the character Omusubiman was previously alluded to but has not been addressed in later stories.

Regarding the specific film Soreike! Anpanman: Yuuki no Hana ga Hiraku toki, no reliable direct information exists that provides specific details about Batako-san's role, actions, or development unique to this particular movie beyond her consistent, general supportive function in the franchise.