Momoko Nonomiya fulfills the role of housekeeper at the Oohara estate, overseeing all household responsibilities. She stands 166 centimeters tall, possessing brown eyes and short brown hair, with physical measurements of 101 centimeters (bust), 61 centimeters (waist), and 92 centimeters (hips). Her typical work attire consists of an apron worn over minimal clothing; she often forgoes underwear during duties for practical reasons related to her sexual availability.

A long-standing childhood friendship connects her to the estate's mistress, Aoi. This bond evolved over time, leading Momoko to transition from casually assisting Aoi to embracing housekeeping as her full-time profession. While competent in household management, her laid-back and carefree nature occasionally results in careless mistakes, which she typically dismisses with laughter rather than distress.

Her hypersexuality is a defining characteristic, with descriptions noting that labeling her a nymphomaniac would be an understatement. She engages freely with multiple partners on the estate grounds and pursues Kenta Fushimi, an art student residing at the mansion, with immediate and persistent attention. She initially views Kenta as a "nice person who helps in various ways," though their relationship deepens over time. This progression culminates in her arranging a date with him, an encounter ultimately interrupted when Kenta is diverted by another woman, Miko.

Her duties extend beyond standard housekeeping to include niche activities like cleaning and cow cosplay, though no further elaboration on these specific roles exists in available sources.