Hitagi Senjougahara is a third-year student of Naoetsu Private High School who is considered to be a frail-looking girl with an "incurable disease" and she is distant from others. In an accidental encounter with Koyomi Araragi, her closely kept secret is exposed, and triggers a life-changing experience. In the course of the series, she receives the nickname Gahara and uses the alias Senshougahara. She is the titular protagonist of three main arcs: Hitagi Crab, Hitagi End and Hitagi Rendezvous and of six minor arcs: Hitagi Buffet, Hitagi Neck, Hitagi Salamander, Hitagi Coin, Hitagi Figure and Hitagi Throwing. Hitagi is a beautiful girl with long purple hair (dark brown in the light novels), blue eyes and a glamorous figure, although she is also considered a "frail" girl due to her lack of participation in school activities. She wears the Naoetsu Private High School uniform the usual way while wearing black thigh-highs and can be seen wearing dresses or similar clothing that cover up to her knees. In later events, she has the sleeves of her uniform rolled up and pinned in place, turning her uniform into a sleeveless blouse and has short hair. Hitagi possesses a sharp tongue and can be quite blunt when speaking to others and while doing so she keeps a straight face making her seem quite frightening. This trait of hers makes interacting with her a challenging task, if not impossible, and is something that Araragi discovers first-hand. In spite of this, she is sincere in everything that she says. She calls herself a tsundere (though she is more of a kuudere) and probably has some understanding of otaku culture, as she once mentions how "moe" Meme's name was to Araragi. She claims that due to her "high strung" nature she is generally a light sleeper. She also seems to have an aversion to kids. She used to have a habit of threatening others, especially Araragi, by using stationary supplies as weapons when feeling endangered or jealous, although grew out of it later on in the series. After the events in Tsukihi Phoenix, she overcame all of her trauma and finally became a completely normal and cheerful girl, chuckling at small things although her sharp tongue is still present, only toned down. She claims that she has an Electra Complex and so, would be too excited to sleep in her father's futon. Hitagi further appears to be knowledgeable about astronomy, as seen during her dates with Aragagi.