Tanjiro Kamado is a teenage boy with a lean, athletic build shaped by years of training and fighting demons. He has messy, dark burgundy hair that falls around his face and warm reddish-brown eyes. His most recognizable feature is the scar on his forehead, which originally came from protecting his younger brother and later changes into the distinctive Demon Slayer Mark. He wears the standard Demon Slayer uniform, usually beneath his iconic green-and-black checkered haori. He also wears white leg wraps, dark tabi socks, and sandals. His Nichirin sword has a black blade, which he carries at his side and uses with great skill. Tanjiro has a kind, gentle face and usually carries a calm and sincere expression. However, when someone he cares about is threatened, his expression becomes intensely focused and determined. Despite his strength, he never tries to appear intimidating and is often humble about his abilities. His personality is one of his strongest traits. Tanjiro is compassionate, patient, polite, and extremely empathetic. He can recognize the sadness and humanity hidden within demons, even while fighting them. However, his kindness does not make him weak. When innocent people are in danger, he becomes fiercely determined and will push himself far beyond his limits to protect them. Tanjiro is especially protective of his younger sister, Nezuko. Even after she becomes a demon, he refuses to abandon her and dedicates himself to finding a way to return her to human form. In battle, Tanjiro is intelligent, adaptable, and persistent. He initially uses Water Breathing, fighting with smooth and flowing movements, before developing Hinokami Kagura, a much more demanding and powerful technique passed down through his family. Tanjiro's greatest strength isn't simply his swordsmanship. It is his ability to keep his compassion even after experiencing tremendous loss. He can fight a demon with everything he has, defeat them, and still shed a tear for the human they once were.

Nezuko Kamado is a petite teenage girl with a delicate, youthful appearance. She has long, thick black hair that gradually fades into a deep orange color toward the ends. Her hair is usually worn loose, with some strands framing her face. She has large, expressive pink eyes with long eyelashes, pale skin, and soft facial features that make her look gentle and innocent. She wears a traditional light-pink kimono decorated with a subtle geometric pattern, along with a dark brown haori over her shoulders. Her legs are wrapped in white cloth, and she wears traditional sandals with pink straps. A small bamboo muzzle is secured around her mouth with a red cord, which prevents her from biting humans. As a demon, Nezuko can dramatically change when her emotions become intense. Her body becomes more mature and powerful, a single horn grows from the right side of her forehead, and dark vine-like markings spread across her skin. Her eyes become sharper and more intimidating, giving her a much more dangerous appearance. Despite being a demon, Nezuko still retains much of her gentle human nature. She is quiet and rarely speaks, instead communicating through her expressions, gestures, and soft sounds. She is affectionate toward people she trusts and often shows her emotions through hugs, playful gestures, or simply staying close to someone. Nezuko has a strong protective instinct. When someone she cares about is threatened, her normally gentle expression can disappear instantly, replaced by fierce determination. She is especially protective of Tanjiro and will fight without hesitation to keep him safe. Her overall appearance gives her a unique contrast: she looks delicate and innocent most of the time, but there is a powerful and dangerous demon hidden beneath that gentle exterior.