Hitagi is described as a beautiful girl with long purple hair depicted as dark brown in the light novel illustrations and striking blue eyes. She possesses a glamorous figure but is often seen as frail due to her minimal involvement in school activities and sports.

At Naoetsu Private High School, Hitagi typically wears the standard school uniform, paired with black thigh-high stockings. Outside of school, she favors dresses and outfits that generally extend to her knees, maintaining a modest and elegant style.

As the series progresses, her appearance undergoes subtle changes. She eventually cuts her hair short and alters her uniform by rolling up and pinning the sleeves, giving it the appearance of a sleeveless blouse.

Hitagi is known for her sharp tongue and blunt manner of speaking, often delivering harsh or intimidating remarks with a completely straight face. This behavior can make interacting with her extremely difficult, as Koyomi Araragi quickly discovers. Despite her biting words, Hitagi is sincere in her speech and rarely says anything she does not mean.

She refers to herself as a tsundere, though her personality more closely aligns with that of a kuudere. Hitagi shows some familiarity with otaku culture, once commenting to Araragi on how “moe” Meme Oshino’s name sounded. Due to her tightly wound nature, she claims to be a light sleeper and also expresses a general aversion to children.

Earlier in the series, Hitagi had a habit of threatening others particularly Araragi by using stationery as improvised weapons whenever she felt threatened or jealous. However, as she grows emotionally, this behavior fades. Following the events of Tsukihi Phoenix, Hitagi overcomes much of her past trauma and becomes more open and cheerful, often chuckling at small things. Nevertheless, her sharp wit remains, though it becomes noticeably more restrained. She also demonstrates an interest in astronomy, a subject she discusses during her dates with Araragi.

Throughout her three years at Naoetsu Private High School, Hitagi shares the same class as Koyomi Araragi, although she rarely interacts with her classmates during that time. Even Tsubasa Hanekawa, despite knowing her from middle school, admits to knowing little about Hitagi’s current situation, relying only on memories of the person she once knew.

In middle school, Hitagi was regarded as an overachiever. She was friendly, excelled academically, and was a standout varsity athlete in track and field. Coming from a wealthy background her father being a prominent figure in a foreign corporation she lived in a mansion but maintained a humble and approachable attitude. Her talents and personality earned her admiration from both classmates and teachers.

During her first year of high school, Hitagi encountered a mysterious supernatural crab that took away her weight, both physically and emotionally. After the incident, she became increasingly reclusive, avoiding contact with others and threatening anyone who discovered her secret, including her former friend Suruga Kanbaru.

Hitagi later reveals that she suffered a near-death experience from an unnamed illness, surviving only after undergoing extensive surgery. This traumatic event led her mother to seek solace in a religious cult. The cult exploited the family’s vulnerability, eventually draining their wealth. A high-ranking cult member later attempted to assault Hitagi; she fought back, seriously injuring him with a spiked shoe. Despite this, Hitagi’s mother sided with the attacker, leading to the collapse of their family. Her mother left, and her father was left to shoulder the family’s debts, which he continues to repay.

Koyomi Araragi
Hitagi’s relationship with Koyomi begins after he accidentally discovers her secret. Initially, she threatens him to protect herself, but over time, they develop a deep emotional bond. Hitagi eventually confesses her feelings to Koyomi, and they begin dating. Their relationship becomes one of the central emotional pillars of the series, marked by trust, honesty, and mutual support, even as they navigate personal traumas and supernatural events.

Tsubasa Hanekawa
Though once acquaintances in middle school, Hitagi and Tsubasa drifted apart during high school. Tsubasa retains a respectful view of Hitagi based on her past as a model student, though they do not have a close relationship during the main events of the story.

Suruga Kanbaru
Hitagi and Suruga were friends in middle school, but their relationship deteriorated after Hitagi’s encounter with the supernatural crab and subsequent withdrawal from others. Suruga once attempted to uncover Hitagi’s secret, resulting in Hitagi threatening her to ensure her silence. Despite the distance that grew between them, traces of their past friendship linger in their interactions.

Meme Oshino
Although they do not have a deep personal relationship, Hitagi holds a level of respect for Meme Oshino for helping Koyomi deal with supernatural problems, including the issue related to her own weightlessness.