Tanjiro travels to the Swordsmith Village to replace his sword because Hotaru Haganezuka is tired of repairing it. Upon arrival, he is taken directly to Tecchin Tecchikawahara, the chief of the village. He reveals to Tanjiro that Hotaru went missing not so long ago. He then brings Tanjiro to the hot springs of the village, to help his body heal. At the hot springs, he meets Mitsuri Kanroji, the love hashira and fellow demon slayer, Genya Shinazugawa. After spending some time with Mitsuri, she tells him that there's a secret weapon hidden in the village that makes people stronger. Tanjiro ponders what it is, but only briefly. After walking around in the forest for a short while, he meets the mist Hashira, Muichiro Tokito arguing with a kid. From a distance, he figures out that he is asking for a key, and sees that he ends up hitting the kid. Tanjiro steps in and stops the Hashira, and in turn gets hit and faints. He wakes up a few moments later and learns that the kid ended up giving Muichiro the key to make him leave. He explains that the key is used to activate a doll, dubbed Yoriichi Type Zero used for training swordsmen, as its power exceeds those of man. Muichiro uses it for training and breaks it a bit, including chopping one of its 6 arms off. This despairs the kid, named Kotetsu. After consoling him, Tanjiro goes to use the doll to train himself, and Kotetsu offers to teach Tanjiro how to fight better.