Okaa-san is the youthful mother of Ai-chan and Imouto-chan. Having married an older partner and given birth young, her appearance often leads to her being mistaken for Ai-chan's older sister. She bears a strong facial resemblance to her eldest daughter, though her hair is longer and smoother, and a bra-fitting specialist noted her bust size as at least an M-cup.

Her personality is consistently laid-back and carefree, marked by an ever-present smile. She displays a nurturing and kind demeanor towards her daughters, actively supporting them through practical help. Her primary role involves tackling household chores like cooking and laundry.

A recurring task in her daily life is repairing her daughters' clothing, specifically reattaching buttons that frequently detach due to the challenges posed by their large bust sizes.

Within the official animated media, she appears in the second season's episodes 1, 7, 11, and 12, plus the associated OVA 1. Across these appearances, her portrayal remains consistent, focusing solely on her established maternal and supportive role within the family unit without significant deviation, backstory expansion, or character evolution.