Nezuko Kamado is the younger sister of Tanjiro Kamado and one of the main characters in the Mugen Train arc. Originally a kind and caring human girl who helped her mother with household chores and looked after her younger siblings, her life was shattered when Muzan Kibutsuji murdered most of her family and transformed her into a demon. Unlike nearly all other demons, Nezuko retains her human soul and willpower, refusing to consume human flesh or blood. As a demon, she wears a bamboo muzzle given to her by the Demon Slayer Giyu Tomioka to prevent her from biting anyone, and she communicates through muffled sounds, gestures, and facial expressions rather than speech, acting in a childlike manner due to amnesia that erased most of her memories except those tied to her family. Her primary motivation is to protect humans, whom she sees as her own family thanks to a hypnotic suggestion placed by Sakonji Urokodaki, and to help her brother Tanjiro in his quest to find a way to turn her back into a human. In the events of the Mugen Train, Nezuko travels with Tanjiro in a specially crafted wooden box that shields her from sunlight. While the other Demon Slayers are put into a deep sleep by the demon Enmu, Nezuko is unaffected and uses her newly awakened Blood Demon Art, called Exploding Blood, to create pink flames that burn through the ropes binding her companions, allowing her to wake them up. She also contributes to the battle by protecting passengers and fighting alongside Tanjiro, Zenitsu, and Inosuke. Her relationship with Tanjiro is one of deep, wordless devotion; she fiercely guards him even at great personal risk. She also forms a strong bond of mutual respect with the Flame Hashira Kyojuro Rengoku, whom she helps and mourns after his death. Over the course of the series, Nezuko grows significantly in power without ever feeding on humans, instead restoring her strength through sleep. Her notable abilities include size manipulation (shrinking to fit inside her box or growing to adult size for combat), rapid regeneration, superhuman strength and speed, and her Exploding Blood, which burns demon flesh and can even neutralize demon poison without harming humans. She later develops a berserk demon form with a horn and vine-like patterns on her skin, and eventually achieves immunity to sunlight, a feat that no other demon has ever accomplished. Nezuko’s unyielding humanity and protective instincts make her a unique demon and a central figure in the fight against Muzan.