It is the Taisho Period (i.e. 1912-1926). Tanjiro Kamado is living a modest but blissful life in the mountains with his family. One day, when he returns from selling charcoal in town, he finds the remains of his slaughtered family in pools of blood after a demon attack. Tanjiro rushes down the snowy mountain with the sole survivor, his sister Nezuko, on his back. But on the way, Nezuko suddenly snarls, turning on Tanjiro.

At Giyu Tomioka's urging, Tanjiro heads for Mt. Sagiri with his sister Nezuko who's 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.

After a desperate fight to the death, Tanjiro prevails over Kyogai. He exits the house to find Zenitsu who had escaped earlier. But it is then that he sees the strange circumstances before him... The battered Zenitsu holding the box containing Nezuko in his arms while the man in the boar's head mask stands in the way with two Nichirin Swords drawn.

Their next destination is to the north-northwest. Tanjiro and Nezuko head towards Mount Natagumo with Zenitsu and Inosuke. This mountain is covered with spider webs and is swarming with innumerable spiders. Leaving the cowering Zenitsu behind, Tanjiro and Inosuke head up the mountain where they run into fellow Demon Slayers entangled in spider webs.

Tanjiro and Inosuke face off against the Father Spider Demon of Mt. Natagumo. Tanjiro unleashes an attack, only to get hurled away by the demon's overwhelming power. Landing near a river, he comes upon the young demon Rui torturing the Sister Spider Demon. When Rui calls their bond of terror and hatred "a family’s bond," Tanjiro is enraged. So begins the battle between Rui and Tanjiro.

Swordsmen in the Demon Slayer Corps known as Hashiras have arrived on Mt. Natagumo. Giyu Tomioka, the Water Hashira, slays the Father Spider Demon with a single strike. Inosuke, thrilled to see such a display of swordsmanship by someone in a totally different league from himself, challenges Giyu to a duel. Meanwhile, Zenitsu lies near death as the poison circulates throughout his body. Just then, the Insect Hashira, Shinobu Kocho appears before him.

When Rui assaults him with his Blood Demon Art, Tanjiro braces himself for certain death. As his life flashes before his eyes, he suddenly remembers his father's dance, the kagura, and unleashes a new, non-Water Breathing attack. Hinokami Kagura Dance. Knowing that he’ll be receiving a simultaneous blow from the demon, he uses his new move to slice off Rui’s head. As Tanjiro crawls towards Nezuko, who lies on the ground, riddled with wounds, someone appears before him.

Seeing Tanjiro try to protect Nezuko even as he collapses triggers memories of Rui’s own past. Once a sickly boy, he became a demon after meeting Muzan Kibutsuji who gave him a share of his blood. But after he turns into a demon, his own parents try to kill him. Ever since then, he has been searching for a family. Seeking a bond that he can never hope to acquire...

After the battle is over, Tanjiro and Nezuko are taken to the Demon Slayer Corps headquarters. This is where the Hashira Meeting between the Corps leader, Ubuyashiki, and the Hashiras, the most powerful swordsmen in the Corps, is to be held. The Hashiras censure Tanjiro for violating the Demon Slayer Corps by protecting a demon. And then, the Wind Hashira, Sanemi Shinazugawa, raises his sword against Nezuko...

As Tanjiro and the others are devoted to their rehabilitation training, the absolute master of the demons, Muzan Kibutsuji, gathers the Lower Ranks of the Twelve Kizuki. The demons, too, are preparing to make their next move. As training draws to a close, Tanjiro has improved to the point where he can fight on equal terms with Kanao. Just then, he receives word of a new mission from his Kasugai Crow.

Due to his strong desire to receive chocolates, Zenitsu seeks advice from teachers Mr. Rengoku and Mr. Tomioka on how to be more popular.

For the past few days, there are rumors of a suspicious person lurking around the school premises. Upon seeing an illustration of the alleged perpretator, Tanjiro notices something…

Flame Hashira Kyojuro Rengoku receives new orders: Travel to the Mugen Train, where over forty people have gone missing, and conduct an investigation. Leaving the Demon Slayer Corps Headquarters, he sets off on this new mission.

The demon that appeared before Tanjiro and Rengoku after they defeated Enmu was the Upper Three, Akaza. While injured and on the ground, Tanjiro is almost attacked by Akaza and narrowly escapes death when Rengoku quickly strikes back. During the intense battle between Rengoku and Akaza, Akaza suggests to Rengoku that he should also become a demon. Rengoku vehemently refuses Akaza's offer, but his injured body is exhausted and being pushed past its physical limits...

The Hashira, Sanemi and Iguro, along with their comrades head to an abandoned castle on top of a mountain for a mission, while Tanjiro is being treated at the Butterfly Mansion for the wounds he suffered at the Swordsmith Village. Later on, the Hashira gather at the Ubuyashiki Mansion to hold a Hashira meeting, where Muichiro reveals how the marks manifested. In an effort to strengthen the entire Demon Slayer Corps from the bottom up, the Hashira Training begins...

Kagaya's Kasugai Crow suddenly appears in front of Tamayo and invites her to the Demon Slayer headquarters — even though she is a demon. Meanwhile, after receiving a letter from Kagaya at the Butterfly Mansion, Tanjiro pays a visit to Giyu, who is not participating in the Hashira Training. At first, Tanjiro is rejected by Giyu but patiently continues to try to talk to him. Giyu, who gives in to Tanjiro's persistence, begins to share the reason why he won't participate in the training.

After talking with Tanjiro, Giyu is able to overcome his past self and decides to join the training. Meanwhile, Tanjiro's wounds have healed enough to join the training, and heads to his first training with the former Hashira, Uzui.

After completing training with Uzui, Tanjiro visits the Tokito residence next. The Demon Slayer swordsmen who have already started the training are dispirited by Muichiro's intense training and harsh words. Tanjiro hears the swordsmen discussing if there's anything they can do about it...

After completing Mitsuri's training, Tanjiro heads to train with Iguro. When he arrives at the training site, Iguro is waiting for him, visibly angry. Will he be able to complete this horrifying training where he'll have to fix his sword skills?

After completing Mitsuri's training, Tanjiro heads to train with Iguro. When he arrives at the training site, Iguro is waiting for him, visibly angry. Will he be able to complete this horrifying training where he'll have to fix his sword skills?

Tanjiro was struggling with Himejima's tasks. Now he finally manages to move the boulder after receiving advice from Genya, whom he meets by chance. With this breakthrough, will Tanjiro be able to overcome Himejima's rigorous training?

During a silent night when the moon shines, Kagaya finally meets Muzan Kibutsuji, who appears at the Ubuyashiki Mansion.