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.

The Demon Slayer Corps... An organization that's been hunting down demons since ancient times. Sakonji Urokodaki starts training Tanjiro for Final Selection, the test for joining the unit. Navigating a mountain riddled with booby traps, dry sword swings, waterfall immersion and breathing techniques... A year later, Urokodaki informs Tanjiro that he has nothing more to teach him, and gives him one last hurdle to overcome in front of a giant boulder.

To pass Final Selection, one must survive for seven days on Mt. Fujikasane where demons captured by the Demon Slayers have been imprisoned. So begins the battle for survival between the young swordsmen and the demons. Armed with the breathing techniques and stances he'd learned from Sakonji Urokodaki, Tanjiro slashes demon after demon. His two years of training have not gone to waste. But just then, a morphed demon appears out of nowhere.

Now split into three, the demons have driven Tanjiro into a corner. It is then that Nezuko attacks. Now that she’s become a demon herself, she’s no longer so weak that she needs protection. His mind made up, Tanjiro follows one of the demons into the swamp now spreading across the ground. Waiting for him there is...

Every time Kyogai, the master of house, plays his tsuzumi, the room spins and Tanjiro struggles. Debilitated by the fractured bones he sustained in his previous battle, Tanjiro tries to fire himself up as he desperately fights on, but he is overwhelmed by Kyogai's Blood Demon Art. Will he find a way to slice off Kyogai's head?

Tanjiro and Inosuke battle the Demon Slayers trapped by spider webs. After slashing the threads and destroying the webs, they head deeper into the mountain. The farther they advance through the forest, the thicker the threads become, and those under their control start moving in ways impossible for a human being. Stopping the Demon Slayers without hurting them isn't going to be easy, but then Tanjiro makes a certain move...

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...

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.

Tanjiro, who's undergoing rehabilitation training at the Butterfly Mansion, works hard to keep up his Total Concentration Breathing techniques all day long. Though at first, he's helpless against Kanao, a swordswoman in his class who's training him, he slowly but surely begins to make some headway. Seeing Tanjiro devote himself to training every single day, Zenitsu and Inosuke resume training as well, but...

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, Zenitsu, Inosuke and Rengoku have fallen into a deep sleep while under the control of Enmu's Blood Demon Art. As Enmu attempts to use his accomplices to destroy the spiritual cores of Tanjiro and his companions in order to defeat them, Tanjiro realizes that he is inside a dream and searches for a way to wake up. In order to awaken from the dream, Tanjiro makes a decision to use his sword to cut into his own neck.

After arriving at the Entertainment District, Tanjiro and his comrades infiltrate each House where Uzui's wives, Suma, Makio and Hinatsuru, work. While working as apprentices and searching for their whereabouts, Inosuke hears that Makio has been shutting herself away from everyone in her room.

Tanjiro and Uzui have been separated by Gyutaro’s Blood Demon Art. As Tanjiro joins the struggling Zenitsu and Inosuke, they manage to decapitate Daki at last thanks to their coordinated barrage of sword strikes. However, when Inosuke tries to run off with Daki’s head, he gets pierced by Gyutaro’s scythe. Uzui has also collapsed, leaving Tanjiro and the others with their backs to the wall.

Tanjiro intervenes during an argument between a pillar and an apprentice blacksmith and learns of the existence of an amazing training method.

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.

Two simultaneous fights continue, Tanjiro, Nezuko and Genya against Hantengu and Tokito against Gyokko. Genya began to show a demonic form. Tanjiro asks him to look for Hantengu's real body, but memories of the past begin to plague Genya.