Hitagi Senjougahara

Hitagi Senjougahara is one of the main characters from the Monogatari anime and light novels.

Hitagi is a third-year student of Naoetsu Private High School. She is considered to be a frail-looking girl with an "incurable disease" and 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.

Appearance
Hitagi is a beautiful girl with long purple hair (dark brown in the novels) and blue eyes. She has 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.

Personality
Hitagi possesses a sharp tongue and can be blunt while still maintaining a straight face when speaking to others. 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 and probably has some understanding of otaku culture, as she once mentiones how "moe" Meme's name was to Araragi.

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.

Trivia

 * Light novel artwork depicts Hitagi with brown hair, unlike the TV series which has her sporting purple hair. It's worth noting that some scenes in the TV series still show her with dark brownish or black hair, though this is mostly during color palette changes in Bakemonogatari.
 * Hitagi's first name is said to be a related to the term "public works". In fact, the only way to write Hitagi's name using kanji is through, which are the kanji for "fertilizer", "field" and "tree" respectively. Meanwhile, the term "public works" is written in kanji as, which are the kanji for "soil" and "tree" respectively. But since Hitagi's name is written using hiragana, this is quite irrelevant.
 * Hitagi's blood type is O.
 * Her surname means "battlefield" in general, but can also mean a certain mythical battlefield between the gods of Mt. Nantai and those of Mt. Akagi.
 * Senjougahara weighs 45 kg based on her body measurements, but was only 5 kg when she was under the influence of the heavy crab, meaning she wasn't literally "weightless", but rather "weighed less."
 * Hitagi was born on July 7th, making her sun sign Cancer aka The Crab.
 * Hitagi's signature weapon, a stapler, is meant to resemble a crab's claws.