Chizuru Hoshino is the mother of Miyako and Hinata Hoshino, married to a husband referenced as absent due to work but never depicted. She actively worries about her daughters' welfare, showing particular concern for Miyako's reclusive nature and social withdrawal, consistently urging Miyako to engage more with others. Chizuru displays a short temper when addressing Miyako's tendencies to spoil children or behave childishly herself, reprimanding her daughter for such actions. One notable instance involved her physically suspending Miyako as punishment after Miyako permitted Hinata and Hana to eat excessive sweets before dinner.

Chizuru curates a collection of family photo albums, readily sharing them with Hinata's friends. These albums include photographs exposing Miyako's past chuunibyou phase, featuring a flashy scarf, eyepatch, and golden contact lenses, much to Miyako's embarrassment when revealed. Chizuru is frequently depicted with a cigarette equipped with a nicotine filter in her mouth. Her interactions primarily involve reacting to her daughters' antics, expressing frustration, or sharing lighthearted family memories. No significant character development or background expansion beyond this maternal role occurs across the series, film, or OVAs.

Physically, Chizuru has brown hair and brown eyes. She remains a consistent parental figure focused on guiding her daughters, especially through corrective measures during misbehavior. While aware of Miyako's social challenges, she addresses them through direct methods.