Hitagi Senjōgahara is a third-year student at Naoetsu Private High School. Initially appearing frail and reclusive due to an "incurable disease," her childhood involved surviving a life-threatening illness through extensive surgery. This event caused her mother to join a cult, leading to the family's deterioration. A high-ranking cult member attempted to rape Hitagi, who defended herself with a spiked shoe. Her mother sided with the attacker, abandoned the family, and left substantial debt, causing Hitagi to become emotionally guarded. During her first year of high school, the supernatural Heavy Stone Crab took away her emotional and physical weight, reducing her to five kilograms. This manifested her avoidance of emotional burdens like regret and sadness while rendering her nearly weightless. Consequently, she isolated herself and threatened anyone discovering her secret. Her initial personality featured a sharp tongue, bluntness, and the use of stationery items like staplers as defensive weapons. She self-identified as a tsundere but exhibited more kuudere traits, maintaining a cold exterior to mask vulnerability. Her development began when Koyomi Araragi accidentally discovered her condition. Through his intervention, she met Meme Oshino, who facilitated the crab's exorcism. This required Hitagi to directly confront her past traumas, leading her to reclaim her emotional and physical weight. She then acknowledged Araragi as her first friend and entered a romantic relationship with him, marking the start of her "rehabilitation." She gradually softened her abrasive demeanor while retaining her forthrightness. In subsequent arcs, her growth continued. During Nisemonogatari, possessive tendencies surfaced as she sought to protect Araragi by confronting Deishū Kaiki, the con artist who exploited her family. Initially resolved to violence, she ultimately chose cooperation with Araragi, signaling increased trust and a shift from isolationist tactics. Her relationship with Kaiki remained complex; she resented his role in her family's ruin but later sought his help to save Araragi from Nadeko Sengoku in Koimonogatari. During this, she displayed unresolved emotional conflict, crying when Kaiki assured his assistance while maintaining pragmatism. By Tsukimonogatari and Owarimonogatari, Hitagi had evolved into a more emotionally open and cheerful individual. She cut her hair short as a symbolic gesture of change, reflecting her shedding of defensive personas. Her sharp tongue persisted but was tempered by genuine expressions of care, particularly toward Araragi and reconciled friends like Suruga Kanbaru. She also demonstrated concern for Tsubasa Hanekawa during the latter's struggles, indicating deeper connections. In Zoku Owarimonogatari, Hitagi's development culminated in her becoming a "completely normal and cheerful girl." She laughs freely and engages more openly, though traces of her direct speech remain. Her reliance on stationery as weapons ceased entirely, symbolizing full integration of her emotional burdens. She maintained her relationship with Araragi and pursued a successful business career, leveraging her rational and strategic mindset. Her journey resolved core traumas, including her grudge against Kaiki, allowing her to function without her former defensive mechanisms. Additional facets include her July 7th birthday, linking her to the Cancer zodiac sign and the crab motif. Her weight stabilized at 45 kilograms post-exorcism, contrasting her earlier five-kilogram state. She also exhibited knowledge of astronomy, often referenced during dates with Araragi.