Chiaki Yoshikawa is the middle sister of the three magical Yoshikawa siblings. She has long, lavender or violet hair that is often tied back with a red ribbon. Her name contains the Japanese word for autumn, aki, reflecting her position as the third child in the family.

In terms of personality, Chiaki stands out as the most sweet-natured and likable member of the cast. She is characterized by a clueless, honest, and sincere demeanor, acting without any guile or malice. This makes her seem somewhat naive but genuinely good-hearted, representing the most normal and approachable of the Yoshikawa sisters. Among the magical sisters, her primary drives are remarkably simple and wholesome: she has a great love for working out, staying fit, and eating food. Her passion for eating is particularly notable, often cited as her main hobby and a defining character trait.

Within the story, Chiaki and her sisters live with their brother, Haruo Yoshikawa, who is initially unaware of magic. The sisters work to keep the existence of magic a secret from him, using measures like memory-erasing hammers whenever he witnesses supernatural events. Chiaki plays a supporting role in this dynamic, assisting her sisters in their various magical endeavors and daily schemes. Her role often involves participating in the comic situations that arise from the intersection of their magical lives and ordinary school life. She is involved in events such as battles with a witch hunter named Marin Nijihara and adventures like using time travel magic. Her key relationships are primarily with her two sisters, the eldest Maika and the youngest Fuyuno, with whom she shares the responsibility of managing the family's magical secrets and dealing with magical guests like the witch Ayumi Mamiya and student council president Yuri Kurosu.

Chiaki does not undergo a significant dramatic character arc but serves as a consistent, stabilizing presence due to her sincerity and lack of complex motives. Her development is subtle, rooted in her unchanging and reliable personality. As a witch, Chiaki is capable of using magic, though the full scope of her abilities is not the central focus of the series. Her main notable abilities are her magical powers, which she uses alongside her sisters, combined with her physical fitness and strength from her love of working out.