Tanjirō Kamado hails from a mountain family of charcoal sellers. As eldest son to Tanjūrō and Kie Kamado, he took on the responsibility of providing after his father's death, regularly journeying to sell charcoal. His father taught him the foundations of Hinokami Kagura, a ritual dance involving specific breathing techniques that induce a plant-like state and heightened perception. A childhood scar marks his forehead from protecting his brother Takeo from a falling brazier.

Returning home one day, he found his family slaughtered by a demon, with only his sister Nezuko surviving, though transformed. Demon Slayer Giyū Tomioka intervened upon witnessing Nezuko's retained humanity and protective instincts toward Tanjirō. Giyū directed Tanjirō to train under Sakonji Urokodaki on Mount Sagiri. Through rigorous training, Tanjirō mastered Water Breathing swordsmanship, passed the Final Selection, and joined the Demon Slayer Corps. Nezuko accompanied him in a protective box, hypnotized to resist human blood.

Tanjirō possesses profound kindness and empathy, extending even to the demons he must kill, acknowledging their former humanity while resolute in his duty. His determination to restore Nezuko and avenge his family fuels him. He exhibits heightened senses, particularly smell, detecting emotions, weaknesses ("opening threads"), and environmental shifts. His combat intuition allows him to devise strategies mid-battle, like feinting attacks or combining weapons. Physically, he has a muscular build, dark red hair with burgundy tips, and eyes with white pupils. His forehead scar evolved into a flame-like Demon Slayer Mark during intense combat. He wears distinct hanafuda earrings depicting a rising sun, a family heirloom linked to Sun Breathing.

Throughout his missions, Tanjirō mastered Water Breathing and integrated Hinokami Kagura—later revealed as Sun Breathing, the original combat style. Key battles include defeating Lower Rank Five Rui alongside Nezuko, where he first merged Water Breathing with Hinokami Kagura; battling Enmu on the Mugen Train with Kyōjurō Rengoku and witnessing Rengoku's death against Upper Rank Three Akaza; and partnering with Tengen Uzui in the Entertainment District to kill Upper Rank Six siblings Daki and Gyutaro, overcoming Gyutaro's poison through Nezuko's Blood Demon Art.

In the Swordsmith Village Arc, seeking repairs for his damaged Nichirin Sword, Tanjirō faced attacks by Upper Ranks Four (Hantengu) and Five (Gyokko). Collaborating with Genya Shinazugawa and Mitsuri Kanroji against Hantengu's emotion-based clones, he executed a lightning-fast strike blending Thunder Breathing principles with Sun Breathing, hinting at style evolution. A new sword forged during the battle enabled him to behead Hantengu's true form. Afterward, Nezuko exposed herself to sunlight, conquering it—an unprecedented feat for demons. This reverted her speech temporarily and made her Muzan Kibutsuji's primary target.

Tanjirō subsequently learned his Hanafuda earrings and Sun Breathing descended from Yoriichi Tsugikuni, the strongest historical Demon Slayer. During the final battle against Muzan, Tanjirō lost an eye and an arm, and Muzan's blood transformed him into a demon. Nezuko, now human due to a cure, helped reverse this transformation. Post-conflict, Tanjirō married Kanao Tsuyuri, settling peacefully with Nezuko and his companions. His right eye remained blinded, and his regenerated left arm retained limited functionality.