Kiyoka Kotobuki is the mother of the series' protagonist, Ran Kotobuki, and a central figure in the Kotobuki family. She is a police officer, working in roles such as a traffic guard, and shares the family profession alongside her husband, Taizo, and her son, Yamato. Despite being the mother of a teenage daughter, Kiyoka is notable for her remarkably youthful appearance, which is a running joke throughout the series, as she looks much younger than her husband and could easily be mistaken for an older sister to her children.

In terms of personality, Kiyoka stands out as a calm, patient, and supportive presence within her family. Unlike her husband, who often clashes with Ran over her lifestyle choices and dreams of becoming a police officer, Kiyoka is rarely upset by Ran's determination to be a Gal. She is consistently portrayed as being very supportive of her daughter's choices and maintains a level-headed and understanding demeanor in family matters. Her role in the story is primarily as a nurturing maternal figure who provides a stable and loving home environment, counterbalancing the more boisterous and explosive temper of her husband.

Kiyoka's key relationships are centered on her family. She is the wife of Taizo Kotobuki, the police chief, and the mother of Ran, Yamato, and Sayo. Her relationship with Ran is defined by patience and acceptance, allowing her daughter the freedom to express herself. With her son, Yamato, she shares the bond of being fellow officers, though her approach to police work and family life is notably more relaxed than his often serious demeanor. The character does not undergo a significant personal transformation or development arc, as she serves as a constant and stabilizing force in the dynamic Kotobuki household. A notable aspect of her character, beyond her police duties, is the ongoing, lighthearted mystery surrounding her age, emphasizing her unexpectedly youthful looks.