Following the fierce battle in the Entertainment District, Tanjiro’s sword is badly chipped, and his swordsmith, Hotaru Haganezuka, refuses to forge a new one. To resolve this, Tanjiro travels to the hidden Swordsmith Village, the secret location where all Nichirin swords are crafted. There, he reunites with the Mist Hashira, Muichiro Tokito, and the Love Hashira, Mitsuri Kanroji, while discovering a mysterious 300-year-old training doll.

The peace of the village is shattered when the Upper Rank demons Hantengu and Gyokko launch a surprise invasion on Muzan's orders to cripple the Demon Slayer Corps by destroying their weapon source. Tanjiro, Nezuko, and the short-tempered Genya Shinazugawa must assist the Hashira in a multi-front battle against Hantengu’s shifting emotional clones and Gyokko’s grotesque art-based attacks. The season concludes with a world-shaking revelation regarding Nezuko’s nature that changes the rules of the war against Muzan forever.