At the urging of a man named Giyu Tomioka, wielding a massive sword that also has a circular saw blade, Tanjiro sets off for Mt. Sagiri with his sister Nezuko, who has been transformed into a demon. One night, Tanjiro picks up the scent of blood coming from inside a temple.
He enters and believes there may be someone injured, but he instead stumbles upon a man-eating demon. When the demon strikes, Tanjiro is able to fight back using his axe, but the strength of the demon is too powerful. Just as the demon is about to finish him off, Tanjiro is saved by none other than.
On his way to Mount Sagiri, Tanjiro asks a nearby farmer if he can take his basket, as well as straw and bamboo, to repair it. The farmer lets him and Tanjiro offers to pay him. He refuses to pay since it’s got holes in it, but Tanjiro asks him to pay him. He again refuses to pay him and even offers him the straw and bamboo for free, but Tanjiro adamantly ignores his refusal to pay.
Annoyed, he tells Tanjiro that he can take it for free again, before he slaps a number of coins into his hand before running away and thanking him as the farmer yells in pain. Tanjiro finds Nezuko in a nearby dirt tunnel; she has dug herself into the ground as well indicating her high aversion to seeing sunlight.
After repairing the basket, he asks whether she can fit inside talking slowly as he doesn’t know if she can understand him. When she shrinks herself to fit inside, Tanjiro lashes the basket to his back. Now able to carry her with her protected from the sun, he makes his way to the mountain, asking for directions from a nearby woman who also warns Tanjiro that people have been going missing as of late, warning him to be careful.
At nightfall, Tanjiro and Nezuko discover a temple in the woods. As he approaches he smells the blood and runs inside. When he opens the doors he freezes on seeing a demon eating several corpses inside, and when he smells the blood he salivates, according to Nezuko.
The demon tells him to stay away or off his turf as Tanjiro stands in one place, shocked by the bloody scene. As they question whether both of them are human, the demon jumps at Tanjiro who cuts his neck with his hatchet. Mildly impressed by the cut, the demon demonstrates his great power of regeneration by healing the deep cut in seconds.
With astonishing speed, the demon vanishes for a moment and surprised at the last moment grabs up Tanjiro, who is not quick enough to react.
Despite the scent of blood, Nezuko resists the urges and runs to save her brother kicking the demon’s head off. Believing at first that she has killed him, the body of the demon tries to grab him, forcing Nezuko to kick him in the body and restrain him. The demon’s head starts talking to him irritated as he happens to be correct on one of them being a demon.
The head sprouts arms and starts attacking Tanjiro, whilst Nezuko gets beaten by her body and is thrown deep into the local forest. With the head of a demon hooked to his hatchet, Tanjiro attacks by headbutting him, stunning the demon with the hard blow. With the head attached, he throws the hatchet into a tree, impaling the head. With one threat eliminated, Tanjiro makes his way to Nezuko. At the edge of a cliff, Tanjiro sees the body slamming Nezuko on the edge of a cliff.
Nezuko grabs her brother before he falls and the body hits hard upon the rocks below; the demon’s head is knocked unconscious feeling the pain of its body. Armed with a knife, Tanjiro sees the head unconscious, but still alive, and prepares to kill it. He rationalizes his decision as it may kill others but he hesitates to kill the demon taking long enough for a man to come behind him.
The man reports to him that he cannot kill it with a knife, gesturing Tanjiro’s attention to a rock. Now forced to smash the head time and time again, Tanjiro freezes in the moment of it. The man catches his scent and notices that he is too good for even to kill demons, thinking that he will not survive as a Demon Slayer.
The demon wakes and attempts to grab Tanjiro as the sun rises and its light burns the demon setting him on fire before he falls back to ashes. He realizes that the demon is now dead from just a little sunlight and runs to find Nezuko, he is relieved to find her inside the basket in the temple safe from the sunlight. After burying the dead in the temple, the man introduces himself as Sakonji Urokodaki, and he surmises that Tanjiro is the boy, Giyu had sent for him.
Tanjiro starts to introduce himself and Nezuko but is cut off by Sakonji with the question of what he plans to do if Nezuko devours someone. Shock by the question, Tanjiro does not answer, and is sternly slapped in the face and reprimanded for thinking too slowly.
Sakonji accuses him for hesitating to kill even a demon and informs him that the right way to respond if Nezuko kills someone is to kill her and then kill himself. “That’s the meaning of travelling with your sister, who became a demon.”
Sakonji warns him that it must never happen, to which Tanjiro now acknowledges the threat. He puts him through a test to determine if he is qualified to join the Demon Slayer Corps by carrying Nezuko and following him. In the middle of the day, Tanjiro pursues Sakonji, who is maintaining a good distance in front of him.
Wondering how old he is and how he is able to be so fast and create little footsteps, Tanjiro struggles to be able to keep up. He apologizes to Nezuko because she is getting battered up inside the basket as he runs asking her to bear with him because patience is all she has known. He recalls when he saw Nezuko fixing her torn kimono. He adds to this his belief that Nezuko will not harm humans and that, as with Sakonji himself, Tanjiro possesses a keen sense of smell. Tanjiro tears up at the memory and vows to do everything that he had hoped for his siblings for her now.
