Chie Rumiko teaches the mixed-age class at Hinamizawa Branch School. Her design parodies Ciel from Tsukihime, featuring blue hair and eyes, a white outfit with a red ribbon and green jewel, and a carried notebook. She exhibits deep dedication to her students' welfare and education, frequently intervening in personal crises—particularly Satoko Houjou's abusive circumstances. She persistently contacts child services and visits the Houjou residence, continuing efforts even after initial failures. During the Great Hinamizawa Disaster, she dies in multiple story arcs, though some timelines show her surviving and relocating to Tokyo.

Her defining trait is an all-consuming obsession with curry: she eats it daily, tends a curry garden behind the school, and reacts with extreme fury to any insult against it, earning the moniker "Curry Demon." This manifests during events like curry competitions where she fiercely defends the dish. In comedic scenarios like Hajisarashi-hen, she wields T-squares as weapons, mimicking Ciel's combat style.

Within Rei's Saikoroshi-hen arc, she inhabits an alternate world without Hinamizawa's cyclical tragedies. Her core personality persists, but subtle differences emerge—like formally calling Satoko "Satoko-san" (reflecting Satoshi's presence) rather than "Houjou-san." She still participates in activities like curry competitions, but in a reality free of the series' central conflicts.

Her background notes she moved to Hinamizawa during the dam conflict to teach at the newly founded school, overcoming education board opposition. She resides in Okinomiya and maintains professional ties with colleagues such as Kyousuke Irie. Spin-offs like Higurashi Daybreak feature alternate Ciel-inspired costumes, and discarded Gou plans briefly considered an antagonistic role for her, scrapped due to her status as a guest character from another franchise.