Chika Itoh is a 12-year-old sixth-grade student who serves as the "straight man" in her friend group because of her ordinary and grounded nature. She has dark brown hair usually tied in a single pigtail and brown eyes, standing approximately 1.45 meters tall. Her personality is defined by practicality, responsibility, and a serious focus on academics; she often prioritizes homework and studies over leisure. This leads others, particularly her friend Miu Matsuoka, to view her as "uptight" when she refuses to play or share homework, and as a "cheapskate" for not buying treats.

Chika lives with her older sister, Nobue Itoh. When their parents are absent, Chika takes on significant household responsibilities, including managing finances to prevent Nobue from spending money on cigarettes and alcohol. Although Nobue describes her as having "no distinguishing traits" and specializing in "being totally generic," Chika demonstrates notable skill in cooking and baking, especially cookies, which her friends frequently request.

Her relationship with Miu involves frequent clashes due to Miu's chaotic behavior, prompting Chika to react with irritation to Miu's antics. However, subtle indications suggest she occasionally finds Miu's humor amusing despite her outward frustration. Chika maintains a pragmatic dynamic with Nobue, balancing sisterly interactions with efforts to curb Nobue's irresponsible habits.

Chika's responsibilities extend beyond academics to domestic duties, reflecting a maturity beyond her peers. She enforces household rules and financial discipline, contrasting Nobue's carefree attitude. Her blood type is A, and her birthday is May 11.