Inside the house, where the rooms spin each time the tsuzumi is played, Tanjiro gets separated from Zenitsu Agatsuma. Without Tanjiro by his side, Zenitsu is overcome by fear and despair as he takes Shoichi through the house. Meanwhile, Tanjiro meets the master of the house, the tsuzumi-playing demon, and an odd-looking man wearing a boar’s head mask.

One of the Twelve Kizuki, a direct subordinate of Muzan Kibutsuji, is here somewhere. When Tanjiro slays the Mother Spider Demon of Mt. Natagumo, he learns that a demon who might hold the key to turning Nezuko back into a human is somewhere in this very forest. With the battered Inosuke in tow, he heads deeper into the forest. Meanwhile, Zenitsu trudges forlornly through the woods only to encounter a spider with a human face.

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.

Ubuyashiki, the leader of the Demon Slayer Corps, finally appears before Tanjiro. He tells him that he will allow Tanjiro and Nezuko to join the Corps. But the Hashiras are unable to accept this decision right away. The Wind Hashira, Sanemi Shinazugawa, slashes his own arm and taunts Nezuko with his blood, trying to get her to show her true colors as a demon.

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.

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.

Tanjiro, Nezuko, Zenitsu and Inosuke join Rengoku on the Mugen Train. Having heard that there may be demons on the train, they are on high alert, but they find themselves falling into a slumber. Within his dream, Tanjiro is reunited with his long lost family. However, it is soon revealed that this is a trap set by Enmu (Lower One).

After waking up from his dream by cutting his own neck, Tanjiro battles Enmu, who is the source of all the turmoil on the train. Enmu appears to be getting pleasure from inflicting pain on the passengers, which only infuriates Tanjiro even more. Tanjiro succeeds in severing Enmu's head, only to discover that Enmu's body is fused with the Mugen Train itself. Tanjiro is backed into a corner, but a freshly-awakened Inosuke comes to assist him and...

After the Mugen Train incident, Akaza visits Muzan Kibutsuji. Guided by a crow, Tanjiro Kamado heads off to the Rengoku residence to convey Kyojuro Rengoku's last messages to his father and little brother. Tanjiro's group return to the Butterfly Mansion.

During the fierce battle with Daki, Tanjiro continues to unleash the Hinokami Kagura, which causes a huge strain on his body. Meanwhile, Inosuke reaches the Belt Demon’s nest and saves people who have been captured. Makio, Suma, and Zenitsu, who have been freed from the belt, join in on the fight. As the ceiling of the nest is broken, Uzui appears wielding his swords.

After Nezuko attempts to attack innocent bystanders as her demon form advances, Tanjiro is finally able to make her fall asleep by singing a lullaby. Meanwhile, another demon emerges out of Daki's body after being beheaded by Uzui - Gyutaro, Daki's older brother and the other form of Upper Six. Uzui must now face both demons, Daki and Gyutaro.

Hantengu's head is slashed by Muichiro and he splits into two clones. Muichiro is blown away by Karaku. Tanjiro, Nezuko and Genya are stunned when the clones split into more clones. Muichiro rescues Kotetsu from a Goldfish Demon.

Muichiro, with the help of air blown by Kotetsu to him, escapes Gyokko's Water Prison Pot. Muichiro finally recalls his tragic past.

Tanjiro continues the fight against Hantengu. Amidst all his injuries and the Superior Four's skill, will he be able to defeat him? As the battle draws to a close, the Demon Slayer Squad must race against time to end the fight before dawn.