Osono is the proprietress of a small bakery called the Guchokipan bakery, also rendered in some materials as Gütiokipänjä, in the seaside town of Koriko. She is around twenty-six years old during the events of the story and is expecting her first child, a daughter named Nono who is born near the end of the film. Osono is the first person in Koriko to treat the young witch Kiki with genuine kindness, offering her a place to live and the practical support she needs to begin her independent life.

Osono was born and raised in Koriko, where her parents ran a bakery called Panya Panya. Her mother was known to the neighborhood as O-yono. After her father died of illness and her grieving mother followed shortly afterward, Osono left Koriko for a time and worked in a port town, where she experienced an unrequited first love. She eventually returned home, reopened the family bakery under the new name Guchokipan, and became known in the neighborhood as Osono the baker. Her husband, Fukuo, is a quiet, mild-mannered baker who grew up as the son of the milk shop that supplied her parents' bakery. The two knew each other from childhood, reconnected after she reopened the shop, and married.

In personality, Osono is warm, frank, and generously good-natured. She laughs easily and speaks directly, and her kindness is practical rather than showy. She is not pushy, and she respects other people's independence while remaining ready to help. Film materials describe her as a brisk, no-nonsense type who does not impose herself on others, and note that she had a somewhat rebellious streak in her youth, which suits her resilient, down-to-earth manner. She is perceptive about people and able to reassure Kiki at the right moments, as when she tells her that black is a color that makes a woman look beautiful, or when she senses Kiki's discouragement after cold treatment from the townspeople.

Osono's motivations are rooted in both practicality and genuine care. She runs the bakery with Fukuo while heavily pregnant and needs extra help, and she takes an immediate liking to Kiki. When Kiki returns a lost item to the bakery, Osono offers her lodgings in the attic room above the shop in exchange for minding the counter and the telephone, with breakfast included. The arrangement gives Kiki a home, a purpose, and a foothold in the city. It is also Osono who sees Kiki's flying as a useful skill rather than a novelty, and it is through her encouragement that Kiki begins the delivery service, using the bakery's telephone to take orders.

In the story, Osono serves as a guardian-like figure and a steady adult anchor for Kiki. She provides the material foundation for Kiki's new life, cares for her when she falls ill by making her warm milk porridge, and becomes concerned when Kiki sinks into depression after losing the ability to fly. She supports Kiki without smothering her or solving her problems for her, allowing the young witch to gain confidence through her own efforts. When Kiki finally regains her flying ability and rescues the boy Tombo from a falling airship, the normally composed Osono is moved to tears, reflecting how deeply she has come to care for Kiki.

Osono's key relationships are with Kiki and Fukuo. With Kiki, she is maternal but respectful, acting as a source of warmth and stability who encourages independence. With Fukuo, she shares a loving and easy partnership; he is largely silent while she is expressive, and they work together as a team. She also has a friendly rapport with Kiki's cat Jiji, who makes himself at home in the bakery.

Osono changes comparatively little over the course of the story, functioning as a stable adult presence, but the nature of her relationship with Kiki deepens as she moves from kind landlady to something close to a second mother. Her own life also advances quietly, as the baby she is carrying is born by the end, completing the family she has built in the same building where she herself was raised. Her history of loss, departure, return, and rebuilding gives her a natural understanding of Kiki's loneliness and her need to find her own place.

Her notable abilities include skilled baking, capable management of a small business, and a practical talent for solving everyday problems. She is perceptive about others, generous with encouragement, and able to balance work, pregnancy, and the care of a young guest without losing her composure. Osono has no magical powers, but her grounding presence and generosity are central to Kiki's ability to find her footing in a new town.