Episode 47

A Sword from Over 300 Years Ago (三百年以上前の刀) is the 47th episode of the Kimetsu no Yaiba TV anime series, and the 3rd episode of its third season.

Plot
After landing a blow on Yoriichi Type Zero, Tanjiro and Kotetsu watch as the head breaks away and reveals a 300 year old sword in the doll. The two become ecstatic at finding such a weapon, with Kotetsu believing Tanjiro should wield it due to lacking one. Tanjiro declines to take the blade but the smith notes that Sengoku period steel is of noted high quality, adding that Tanjiro being the one to reveal it should use it. They eagerly unsheathe the blade but quickly become downtrodden to see the sword severely rusted. Kotetsu apologizes for exciting Tanjiro, who accepts with tears of disappointment in his eyes. Suddenly, loud footsteps shake the ground; they turn to see Hotaru Haganezuka himself, now extremely muscular, approaching them and stating that the sword should be left up to him. Tanjiro and Kotetsu try to pull it away from the older swordsmith, confused by his statement and believing it should be Kotetsu’s, but Hotaru continues insisting on taking it.

Tanjiro mentions that he had been looking for him but the smith does not answer him, eventually pulling the blade away to shove the two to the ground. Confused by the man’s immature antics, they are joined by Kozo Kanomori, who promptly demonstrates that by tickling Hotaru’s sides, it will exhaust and calm him down for a time. With the eccentric swordsmith downed, Kozo talks to Tanjiro and explains that Hotaru had secluded himself to the mountains in training, in order to make a blade that would not break for him. He adds that Hotaru appreciates Tanjiro believing in him to make a sword as other Demon Slayers dislike him, which Kotetsu chalks up to his poor socializing skills.

Hotaru then awakens and exuberantly declares that he will polish the rusty blade, to which Kotetsu notes that he could have said so in the beginning, causing the muscular smith to angrily grab him; Tanjiro and Kozo quickly tickle him into exhaustion to save the boy. Before leaving, Hotaru provides Tanjiro with an alternate blade to use for the time being, to which the swordsman is thankful of.

At the village, Tanjiro speaks about Hotaru mentioning that the extensive polishing he will undertake is so intense, it has killed people; he grows worried for his safety and notes that even he is not allow to watch. He relays his concerns to the nearby Genya, who does not care about his situation and demands he do not speak to him as a friend. Tanjiro is confused by his denial of friendship, to which Genya explains that he had broken his arm at Final Selection, though the former states that it was due to hitting a girl. While watching him speak, Tanjiro remembers that Genya was missing a tooth, which he vehemently denies; he pulls out the missing tooth as he wanted to return it, disgusting Genya and causing him to kick him out of his room.