Nezuko Kamado originated as a human, eldest daughter of the mountain-dwelling Kamado family. She supported her mother in household tasks and prioritized her younger siblings' welfare above her own, sacrificing personal comforts like new clothing to ensure they were fed. Her existence shifted irrevocably when Muzan Kibutsuji slaughtered her family, sparing only her brother Tanjiro while transforming her into a demon. Initially succumbing to demonic bloodlust, she attacked Tanjiro but swiftly regained consciousness to shield him from demon slayer Giyu Tomioka, igniting her resistance against her new nature. Tanjiro transported her in a sunlight-proof box to train under Sakonji Urokodaki. During Tanjiro’s two-year preparation for the Demon Slayer Corps Final Selection, Nezuko remained in prolonged slumber. Urokodaki implanted hypnotic suggestions reinforcing that all humans were family to protect and all demons were enemies to destroy. Merged with her innate resolve, this allowed her to reject human flesh entirely, regenerating solely through sleep. Upon waking, she exhibited childlike mannerisms, fragmented memories limited to her family, and nonverbal communication—yet retained human emotional expressions like smiling and crying. Her demon form manifested rare traits, including accelerated growth during combat or healing. Critical transformations emerged in battles: against Upper Rank demon Daki, she entered a berserk state marked by increased height, a forehead horn, vein-like skin patterns, and heightened power, though control diminished until Tanjiro’s lullaby restrained her. Confronting Upper Rank Four Hantengu in the Swordsmith Village, sunlight initially disintegrated her before she spontaneously developed total immunity—a centuries-sought achievement of Muzan’s. This reversion partially restored her human eyes and hands, and gradually returned her speech; she later articulated words clearly after hearing them. Her core combat skill, the Blood Demon Art: Pyrokinesis, ignited her blood into pink flames upon air contact. These flames incinerated solely demons and demonic matter, sparing humans—proving pivotal against foes like Lower Rank Five Rui’s threads or Upper Rank Six Gyutaro’s poison in slayers’ blood. She wielded exceptional strength, speed, and regeneration, fighting via kicks and clawed nails, recovering from severe wounds like dismemberment or decapitation. Despite demonization, her kindness, protectiveness, and self-sacrifice endured. She defended Tanjiro and allies such as Zenitsu and Inosuke against lethal strikes, extending protection beyond hypnosis to demon allies Tamayo and Yushiro, seeing her late mother and brother in them. Compassion surfaced when she resisted Sanemi Shinazugawa’s Marechi blood provocation by recalling her human kin. In the Hashira Training Arc, Nezuko’s sun immunity made her Muzan’s prime target, confining her to the Butterfly Mansion or Urokodaki’s care. She briefly met Zenitsu and Inosuke, accidentally dubbing the latter "Imosuke" to Zenitsu’s irritation, and ingested Tamayo’s medicine for her eventual human reversion. Separation from Tanjiro during training emphasized her vulnerability. During Muzan’s final defeat, Nezuko sensed Tanjiro’s peril from a safe location and raced to him. After Muzan’s fall, he demonized Tanjiro. Nezuko intervened physically, enduring her brother’s assaults while clinging to him, aiding the appeal to his humanity alongside allies. Her blood became essential in the antidote weakening Muzan and purging his influence from Tanjiro. Post-conflict, she reverted fully to humanity. Her restored form kept flame-orange hair tips—later inherited by descendant Toko—and regained all memories and personality, though the transition overwhelmed her, triggering uncontrollable tears. She resumed a demon-free human existence.