Okan is the mother of Hiromu Arakawa in the anime Hyakushō Kizoku and one of the most central figures in the Arakawa household. Like her husband and children, she is depicted as an anthropomorphic cow, with a distinctive curl of hair on top of her head and an apron bearing the word Okan. Her name is a familiar Japanese way of saying mother, which is how her daughter refers to her. Within the family farm, she holds the position of executive director, meaning she is responsible for much of the farm's administrative and organizational work on top of her duties in the home.

The family she was born into lived on a small livestock farm that was located very close to the Arakawa home, so close that the two properties could be reached by following a river that ran through the land. That farm raised dairy cows and a small number of chickens. After marrying into the Arakawa family, she raised five children, including Hiromu, the fourth daughter, who later became a manga artist, and an eldest son who became a veterinarian. Her daily life has been shaped by the routines of dairy farming and crop cultivation, with milk and potatoes among the farm's main products.

In terms of personality, Okan is portrayed as pragmatic, tough, and direct. She has a dry sense of humor and a no-nonsense attitude toward difficulties, and she treats extreme situations such as escaping animals, severe weather, or dangerous incidents as ordinary problems that simply have to be managed. She is just as physically hardy as her husband, but she is the calmer and more grounded of the two, acting as the stabilizing force that keeps the household running while the rest of the family deals with the more chaotic side of farm work. She embodies the tireless work ethic of a farming wife and expects everyone around her to contribute their share of labor without complaint.

Her motivations come from the practical demands of farm life. Because dairy farming cannot be postponed, she is driven by the need to keep the farm and the family functioning day after day. She holds firmly to the values of hard work and self-reliance, and she does not accept excuses from her children when there is work to be done.

In the story, Okan appears mainly through Hiromu's recollections of childhood and daily life on the farm. She plays a leading role in an episode of the second season devoted to her and her mother-in-law, which examines the kind of work performed by the wife of a farming household, work that often goes unrecognized. Her own background as a farmer's daughter, her marriage into the Arakawa family, and her years of supporting the farm are all presented as part of that larger picture of rural life. She also serves as a counterweight to her daughter's complaints about field work. When Hiromu tries to avoid helping during the busy season, Okan tells her that she continued driving a tractor while pregnant, that she did not stop until labor pains began, that she then drove herself to the hospital, and that the delivery was quick and easy. The story is presented as the reason no one in the family can argue with her about hard work.

Her relationships help define the character of the household. With her husband, the patriarch of the Arakawa farm, she forms a complementary partnership in which her sensible nature keeps his more unpredictable impulses in check. With her mother-in-law, the grandmother, she shares a bond built on long years of duty and care. In the episode focused on the two women, the elderly grandmother expresses gratitude to her before dying peacefully during the agricultural off-season, having already prepared her own memorial photograph, and the moment makes clear how much the older woman valued her. With her children she is firm and demanding, but her actions consistently show her deep commitment to their wellbeing.

Okan does not change dramatically over the course of the anime. She remains a steady, unchanging presence, and the deepening of her character comes through the accumulation of stories about her past, her physical strength, and the quiet respect her family holds for her. Her notable abilities are entirely practical: she can handle nearly any task on the farm or in the house, from managing operations and paperwork to heavy physical labor, and her endurance is shown to be considerable even by the standards of her own family. Her role throughout the story emphasizes the essential contribution of women to the running of a farm.