Himawari Furutani serves on the student council at Nanamori Middle School. She possesses collarbone-length azure blue hair, typically styled in two small front pigtails secured with a dark brown headband, gold eyes, and a developed physique for her age, with her large breasts being a recurring source of self-consciousness and teasing. Her speech is consistently formal, polite, and feminine, reflecting a mature demeanor.

She acts as the protective older sister to Kaede Furutani, cooking her meals—including favorite dishes—and discreetly monitoring activities like Kaede's first errand. Himawari also masks her own dislike of bell peppers to set a positive example. Her personality shifts dramatically around childhood friend Sakurako Ōmuro, sharing a complex, tsundere-like dynamic. They frequently bicker, with Himawari often responding to Sakurako's provocations with physical retribution like kicks or throws, yet underlying care persists. She assists Sakurako with homework, shares walks home due to living across from each other, and participates in joint activities like camping trips where they exchange food. Their history includes a close childhood bond, evidenced by a make-believe wedding orchestrated by Sakurako's sister Nadeshiko.

Academically diligent but physically uncoordinated, Himawari struggles in PE, causing anxiety before fitness tests—a contrast to Sakurako's athleticism that fuels further teasing. However, extreme stress or Sakurako's antics can trigger brief surges of physical strength. She excels in domestic skills like knitting, demonstrated when teaching Chinatsu Yoshikawa to knit a scarf, and cooking, preparing meals for Kaede, collaborating with Yui Funami on lunch for a flower-viewing trip, and baking cookies with Chinatsu. Her body image concerns manifest in actions like a three-day diet upon believing she gained weight, halted when Sakurako and Kaede reassure her the change was due to breast growth.

In wider social interactions, Himawari maintains friendly relationships with Amusement Club members. Akari Akaza expresses admiration for her physique, while Chinatsu seeks her help with tasks like Valentine’s Day gifts, prioritizing this over Sakurako’s homework assistance. She also trains with Yui for physical challenges. Her appearances span the main series, the *Nachuyachumi!* OVA—where she joins the camping trip and engages in typical banter with Sakurako—and the *Ōmuro-ke* spin-off. In *Ōmuro-ke: Dear Friends*, she visits the Ōmuro home to retrieve a notebook from Sakurako and notices Nadeshiko’s new necklace.