Tanjiro Kamado grew up in a mountain-dwelling charcoal-selling family as the eldest son, shouldering responsibility for supporting his parents and five younger siblings. A childhood incident shielding his brother Takeo from a falling kettle left a burn scar on his forehead. His father, Tanjuro, taught him the Hinokami Kagura ritual dance and its associated breathing techniques, which became the foundation of his combat abilities. A demon attack shattered their peace, killing all but his sister Nezuko, who was transformed into a demon. This tragedy ignited his quest for vengeance and a cure for Nezuko.

Encountering demon slayer Giyu Tomioka, who initially tried to kill Nezuko, Tanjiro fiercely defended her. Impressed by Nezuko's resistance against harming humans and Tanjiro's resolve, Giyu directed them to trainer Sakonji Urokodaki. Under Urokodaki's rigorous mentorship on Mount Sagiri, Tanjiro honed Water Breathing swordsmanship and survived the Final Selection trial. During this test, defeating the Hand Demon transformed his forehead scar into a flame-like Demon Slayer Mark. He joined the Demon Slayer Corps, adopting their uniform while retaining his checkered haori and hanafuda earrings.

Tanjiro possesses heightened physical capabilities: exceptional endurance, strength gained through training, and a keen sense of smell enabling him to detect environmental details, emotions, and combat openings. His fighting style blends Water Breathing with Hinokami Kagura (later identified as Sun Breathing), accessed through ancestral memories during battles. This synergy allowed him to behead powerful demons like Enmu, fused with the Mugen Train, and the Upper Rank Six duo Daki and Gyutaro in the Entertainment District. His tactical adaptability and repetitive action technique overcame opponents like Rui and Akaza.

Personality-wise, Tanjiro radiates compassion, often empathizing with demons' suffering before delivering final blows and praying for their souls. This contrasts with incandescent fury toward cruelty, especially against Muzan Kibutsuji or witnessing demons like Daki harm civilians. He values honesty and teamwork, though shows impatience with cowardice or rudeness from allies like Zenitsu Agatsuma and Inosuke Hashibira. His protective nature extends beyond Nezuko to comrades and innocents, driving him to accept missions like infiltrating Yoshiwara alongside the Sound Hashira Tengen Uzui to rescue missing persons.

Throughout his journey, Tanjiro sustained severe injuries, including a poisoned eye wound and a severed arm during the final battle against Muzan. Temporarily becoming a demon from Muzan's blood led to regeneration, yet left permanent impairments: blindness in his right eye and limited mobility in his left arm. Post-conflict, he married Kanao Tsuyuri and had descendants, including Sumihiko Kamado. His legacy endured through future generations preserving his earrings and values.