A Sword from Over 300 Years Ago

This is the 47th installment of the anime and the third chapter of its third season, adapting material from chapters 105 through 107. When Tanjiro finishes his bouts against the mechanical training doll Yoriichi Type Zero, its head splits open to reveal a centuries-old sword sealed within. The young smith Kotetsu urges Tanjiro to claim it, though the recovered weapon turns out to be deeply corroded. The eccentric craftsman Hotaru Haganezuka soon arrives to carry the rusted blade away for restoration, lending Tanjiro a spare in the meantime. As the day passes, the demons Gyokko and Hantengu slip into the settlement, and a sudden assault forces Tanjiro and the Mist Hashira into a desperate defense.

The hidden blade

The doll's broken head exposes a weapon forged during the Sengoku era, but rust has ruined its surface. Hotaru, now heavily built from secluded mountain training, insists on taking the sword to apply a punishing polishing method passed down through his family. Kozo Kanamori reveals that the smith retreated to forge a blade that would never shatter, doing so out of gratitude toward Tanjiro for believing in him.

Genya and the demons close in

Tanjiro tries to befriend Genya Shinazugawa, who rebuffs every gesture, still resentful over a broken arm at Final Selection. Meanwhile Gyokko devours a smith and Hantengu hides nearby, both intent on crippling the Corps by razing the village.

The first clash

Hantengu crawls into Tanjiro and Muichiro's room. After Muichiro beheads him, the demon splits into Sekido and Karaku, who wield lightning and wind. Genya intervenes with a Nichirin shotgun, but more manifestations appear, and a winged demon hurls Tanjiro from the air with a sonic strike.

The episode's eyecatchers are loose reworkings of chapter 106's cover art. Several anime additions appear, including a scene where Tanjiro styles Nezuko's hair to resemble Mitsuri's, which draws on a volume extra, and a moment of Genya retrieving his completed Nichirin sword that has no manga equivalent. The anime also clarifies that Nezuko's advanced demonic form risks pushing her toward a full, uncontrollable transformation, and it shows Genya firing his shotgun one barrel at a time rather than both at once.