At Giyu Tomioka's urging, Tanjiro heads for Mt. Sagiri with his sister Nezuko who has been turned into a demon. During the night, Tanjiro catches the smell of blood from inside a temple. He enters, thinking that someone might be hurt, only to come upon a man-eating demon. When the demon attacks, Tanjiro manages to fight back with his hatchet, but the demon's strength is overwhelming. Just as the demon is about to finish him off, Tanjiro is saved by none other than...
Tanjiro buys a straw basket, planning to carry Nezuko in it so they can keep heading to Mt. Sagiri during the day and keep her out of the sun. That night they find a temple but Tanjiro smells blood and they burst inside to find a demon feeding on several humans. The demon attacks Tanjiro while Nezuko stares at the human bodies, salivating. Nezuko turns away and kicks the demon's head off. The body attacks Nezuko while the head attacks Tanjiro. After disabling the head he pursues Nezuko and knocks the demon body off a cliff. The demon's body dies when it falls. An old man, Sakonji Urokodaki, prevents Tanjiro from stabbing the pinned head, as that is not enough to kill it, but Tanjiro hesitates to smash it. Urokodaki notices, but thinks Tanjiro won't work, no matter what Giyu thinks. The sun rises and the demon is vaporized. Urokodaki berates Tanjiro for his hesitation, stating his resolve is weak. He warns Tanjiro letting Nezuko kill an innocent is the worst possible thing, and tests him to see if he is fit to be a member of the Demon Slayers Corps. After going for a long run, he has Tanjiro leave Nezuko in a cabin and climb a mountain. He tells Tanjiro to make it down before sunrise. The mountain is booby-trapped though. Tanjiro uses his sense of smell to find the booby traps, which still have the scent of the person who laid them, letting him return in time. Urokodaki recalls the letter he recieved from Giyu about the siblings, and Giyu's request he train them. He accepts Tanjiro as his student.
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