Okan is the mother of Hiromu Arakawa, the author and central figure of the autobiographical anime Hyakushō Kizoku, and she serves as the executive director of the Arakawa family farm. Like the rest of the immediate family, she is depicted as an anthropomorphic cow, distinguished by a curl of wavy hair on the top of her head, similar to an older woman's perm, and by an apron with the word Okan written on it. Her own background is also rooted in farming. Her family home was located only three houses away from the Arakawa household, and her relatives were livestock farmers who mainly raised dairy cows along with a small number of chickens. The two households were close enough that one could reach them quickly by following the river that ran through the properties.

In terms of personality, Okan is portrayed as sensible, capable, and remarkably hardworking. She is the practical backbone of the Arakawa household and farm, managing the domestic side of the operation while also taking part in heavy physical labor. She frequently serves as the calm, steady presence who keeps the more eccentric members of the family in check, particularly her husband, whose unpredictable and reckless behavior she counterbalances. The series repeatedly emphasizes her versatility, showing that she is able to handle nearly any task required on the farm or in the home, and she is described as someone who works extremely hard at everything she does.

Her motivation is closely tied to sustaining the family farm and household. The household operates under a strict work ethic, and Okan embodies that principle through her constant labor and sense of responsibility. Her efforts are presented as essential to keeping the farm running smoothly over many years.

In the story, Okan is a supporting character who appears throughout the series' vignettes about daily life on the farm. One episode of the second season centers on her and the grandmother, drawing attention to the often overlooked work done by women married into farming families. Through these segments, her role in the narrative is to illustrate the endurance, skill, and quiet strength required to maintain a family farm, as well as the vital contribution of women to agriculture.

Her key relationships are with her husband and her children. She is the wife of the character referred to as Father and the mother of five children, including Hiromu Arakawa, who is the fourth daughter of the family, and an eldest son who became a veterinarian. Her relationship with her husband is defined by her role as the stable, sensible counterpart to his wilder impulses, while her relationship with her children is conveyed through the demanding yet caring environment of the farm.

Okan does not undergo major personal change over the course of the series. Her character remains largely consistent, representing the enduring stability and labor needed to keep a family farm operational across generations. Her development is instead expressed through the gradual revelation of her competence and the breadth of her abilities.

Among her notable abilities are her capacity to handle both domestic duties and demanding farm work, her managerial role as executive director of the farm, and her physical toughness. One anecdote in the series recounts that she continued operating a tractor until labor pains began shortly before Hiromu Arakawa was born, highlighting the same resilience and dedication that define her throughout the series.