Iori Utahime is a character who serves as a teacher at the Kyoto Prefectural Jujutsu High School, holding the rank of a semi-grade 1 jujutsu sorcerer. She is recognizable by her traditional miko attire, which consists of a white kimono top and red hakama pants, and a distinct horizontal scar on the right side of her face that crosses over the bridge of her nose. During her own student days, which are depicted in flashbacks, she did not have this scar, indicating she sustained the injury at some point after her graduation. In her youth, she wore her long black hair in two ponytails, but as an adult she typically wears it down with a large ribbon and short strands framing her face.

As a person, Utahime is generally portrayed as a calm, sincere, and diligent individual who takes her responsibilities seriously. She is a dedicated teacher who genuinely cares for the well-being and safety of her students, such as Kasumi Miwa, Mai Zenin, and Momo Nishimiya. According to official supplementary information, all of her students hold a deep affection for her, reflecting her compassionate and responsible nature as an instructor. Despite her composed demeanor, she has one notable point of consistent agitation: Satoru Gojo. She is Gojo's senior by three years, a fact she often reminds him of, but his constant teasing and mocking remarks about her strength easily provoke her. Her genuine dislike for him is a recurring dynamic, and Gojo is even listed as her primary source of stress. Conversely, she maintains a close and caring friendship with her contemporary, Shoko Ieiri, whom she has often encouraged to quit smoking out of concern for her health.

Utahime's role in the story is primarily that of a support-oriented ally rather than a front-line combatant. She first appears as the supervisor for the Kyoto school during the Kyoto Sister School Exchange Event, where she is tasked by Gojo with helping to investigate a mole within the jujutsu world. During the Shibuya Incident, she leads her students to provide backup for the Tokyo sorcerers. Later, in the final arc of the manga, the Shinjuku Showdown, her abilities become critically important. Before Gojo's battle with Ryomen Sukuna, she performs a long ritual to prepare her cursed technique. When Gojo launches his attack, her technique amplifies the power of his Hollow Purple to two hundred percent of its normal output, giving him a crucial opening. Subsequently, she also aids Yuji Itadori by guiding Nobara Kugisaki to use a binding vow on one of Sukuna's fingers, which enables a remote assist that helps land a decisive blow against the King of Curses.

Her primary ability is her innate cursed technique, named Solo Forbidden Area. This technique does not directly harm an enemy but instead temporarily amplifies the total cursed energy and output of any willing target within its range, including herself. By fully embracing and performing ritualistic steps, such as hand signs, dancing, music, and chanting incantations, she can elevate the technique's effectiveness, reportedly boosting an ally's power to one hundred and twenty percent of their normal capacity. Because the activation requires significant preparation time and ritual, she is most effective when paired with allies who can protect her while she performs it, highlighting her role as a force multiplier in high-stakes battles. Her name contains a subtle hint about her character, as "Utahime" translates to "songstress" or "diva," which relates to both her talent for singing and the vocal components required for her cursed technique.