The landlady of the Hidamari Apartments is the owner and manager of the apartment building where the main characters live. Her full name and exact age are not revealed, and she is consistently referred to as Ooyasan, meaning landlady. She is a young woman with a straightforward, unpretentious demeanor. She is a heavy smoker who favors a particular brand of cigarettes and frequently resolves to quit, though she rarely succeeds. She also enjoys drinking alcohol and is often shown consuming it even during the day. Despite these habits, she is a warm and generous figure who genuinely cares for the well-being of her tenants.

Her background is touched on only lightly. During her own school days, she wrote in a yearbook that her dream career was to become a stewardess, indicating that she never initially planned to become a landlady. How she came to own the Hidamari Apartments at a relatively young age is not explained. She is not a graduate of the art track herself, which sets her apart from most of the residents she accepts into the building.

Personality-wise, she is easygoing, big-hearted, and somewhat disorganized. She has a tendency to be careless with practical matters, such as taking days to locate a spare key from a cluttered closet or failing to complete renovations on time. Rather than raising the rent, she simply lowered the rent for one tenant whose room had a leaky ceiling she could not repair. However, this laid-back nature is balanced by a strong sense of responsibility. She works multiple part-time jobs to support herself, since the rent from the apartments alone is not sufficient. Her tenants often see her as a reliable, fatherly presence within the Hidamari Apartments family.

Her motivations center on maintaining a comfortable, welcoming home for the students who live under her roof. She keeps the building exclusive to female students from the nearby Yamabuki High School, especially those from the art department, and she has a friendly rapport with the school principal and teachers. She socializes with the girls on a casual basis, occasionally bringing them gifts such as watermelons or tomato plants, and she once covered a batch of soba noodles for them. She also has a playful side, sometimes assuming the role of a detective when odd occurrences happen in the building.

In terms of key relationships, she interacts with all the residents as a supportive figure. She is particularly close to the former tenant Misato, who had a similar energetic personality and was said to be unable to talk back to the landlady. She has a respectful acquaintanceship with the principal of Yamabuki High School and with the teacher Yoshinoya. The students view her with affection, though they also recognize her quirks and occasional forgetfulness.

The landlady shows little overt development across the series, functioning more as a stable background presence. Her role is primarily to provide a safe and relaxed environment for the girls, intervening only when necessary and otherwise allowing them to live their daily lives freely. She embodies a blend of maternal care and carefree independence, often riding her scooter around town and spending her spare time fishing.

Her notable abilities include her resourcefulness in managing the building on a tight budget, her skill at riding a scooter, and her ability to juggle multiple jobs while still finding time to interact with her tenants. Her most characteristic trait is a combination of generosity and a slightly messy approach to life that somehow works because of her genuine kindness. She is not a central driver of the plot, but the atmosphere of Hidamari Apartments would be incomplete without her steady, unflappable presence.