Tanjiro Kamado is a kind-hearted and intelligent boy who lives with his family in the mountains. He became his family’s breadwinner after his father’s death, making trips to the nearby village to sell charcoal. Everything changed when he came home one day to discover that his family was attacked and slaughtered by a demon. Tanjiro and his sister Nezuko were the sole survivors of the incident, with Nezuko being transformed into a demon, but still surprisingly showing signs of human emotion and thought. After an encounter with Giyū Tomioka, the Water Hashira of the Demon Slayer Corps, Tanjiro is recruited by Giyū and sent to his retired master Sakonji Urokodaki for training to also become a demon slayer, beginning his quest to help his sister turn into human again and avenge the death of his family.

After two years of strenuous training, Tanjiro takes part in a formidable exam and is one of the few survivors to pass, officially making him a member of the Demon Slayer Corps. He begins his work of hunting down and slaying demons alongside Nezuko, who has been hypnotized to bring no harm to humans and who occasionally helps him in battle. One of Tanjiro’s assignments brings him to Asakusa where he encounters Muzan Kibutsuji, the progenitor of all demons and the one who murdered his family. He also meets Tamayo and Yushiro, demons who are free from Muzan’s control. Tamayo and Yushiro ally with Tanjiro and begin to develop a cure for Nezuko, though it will require Tanjiro to supply Tamayo with blood from the Twelve Kizuki, the most powerful demons under Muzan’s command.

Continuing his missions, Tanjiro meets Zenitsu Agatsuma and Inosuke Hashibira, fellow survivors of the exam with whom he forms an unlikely team during a battle with the former Lower Rank Six of the Kizuki. The group soon face off against Lower Rank Five of the Kizuki, although Tanjiro unlocks a mysterious ability called “Hinokami Kagura”, they are ultimately outmatched; they are rescued by Giyū and Insect Hashira Shinobu Kocho and brought back to headquarters. There, the Kamado siblings partake in a council between Kagaya Ubuyashiki, the leader of the Demon Slayer Corps, and the Hashira, the Corps’ most elite members, who (with the exception of Giyū) do not believe that Nezuko should be allowed to live. However, Kagaya nonetheless manages to convince them to accept her. With this agreement, Tanjiro begins to work alongside the Hashira, where he encounters significantly more resistance from the demons. Alongside the Hashira and Corps members, Tanjiro takes part in numerous harrowing battles against the Kizuki, which they survive by narrow margins while also taking losses of their own, including the death of Flame Hashira Kyojuro Rengoku and retirement of Sound Hashira Tengen Uzui. During a battle in the Swordsmith Village, Tanjiro meets Genya Shinazugawa, the younger brother of Wind Hashira Sanemi Shinazugawa, who has the mysterious ability to temporarily become a demon by eating demon flesh. It is also discovered that Nezuko is invulnerable to sunlight, a discovery that makes her the prime target of Muzan, who has long sought a way to overcome the sun and thus become the ultimate being. Tanjiro also learns that his Hinokami Kagura is descended from Sun Breathing, the original breathing style invented by Yoriichi Tsugikuni, the first and strongest demon slayer, and develops it to prepare to fight Muzan.