Chika, Sae's younger sister by about two years, starts as a middle school student at Maezawa Middle School before advancing to a local public high school. She continues living with her parents, contrasting with Sae's choice to study art at the more expensive Yamabuki Art High School; this reflects Chika's disinterest in pursuing art or literature professionally.

Physically resembling Sae, Chika shares a similar hair color and style, though her hair and eyes carry a distinct lavender hue. She typically wears a hairclip. Personality-wise, Chika occasionally displays immaturity, like her crush on a famous Kabuki actor, and enjoys teasing Sae during visits to Hidamari Apartments. Despite this, she supports Sae's literary ambitions and actively reads her fiction.

Underlying tension exists in Chika's relationship with Sae, partly due to Sae attending Yamabuki. Chika resented Sae's consideration of choosing a college based on easing family financial burdens. She often secures invitations to visit Hidamari Apartments without consulting Sae first, causing Sae discomfort. Nevertheless, the other Hidamari residents welcome Chika and sometimes invite her independently.

During the *Sae & Hiro's Graduation Arc*, Chika appears alongside the main residents for Sae and Hiro's university exams. She participates in group activities, such as preparing meals for Hiro and offering encouragement, highlighting communal support for the seniors while maintaining her role as Sae's occasionally intrusive yet caring sister. Chika's background includes playing in her middle school band, and she is straightforward, openly mocking unusual sights like the shape of the principal's head.