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.

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.

When day breaks, there are only four swordsmen left standing after the seven-day battle. The guides who greet Tanjiro and the other survivors explain the Demon Slayer Corps system. All four are issued uniforms and Kasugai Crows as messengers, after which they must select the ore for their own Nichirin swords. After gazing hard at each lump of ore, and using his keen sense of smell, the one Tanjiro chooses is...

Tanjiro is now clad in the uniform of the Demon Slayer Corps. His Nichirin Sword on his hip, and Nezuko, now awake, in a special box made by Urokodaki on his back, he heads out for his first assignment. A town to the northwest where girls have been vanishing nightly. There, Tanjiro meets Kazumi, haggard with worry after his girlfriend's been abducted. Though he does catch the scent of a demon nearby, there's just no demon in sight. Tanjiro is sure that a demon is behind this sinister incident...

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...

It was two demons named Tamayo and Yushiro who came to Tanjiro’s rescue. Using the “Eyeblind” spell, Tamayo guides Tanjiro and Nezuko to her house. There, through his conversation with Tamayo, Tanjiro learns that there is a way to return demons to human form. Just then, two demons in pursuit of Tanjiro locate the house and unleash a furious assault...

Tanjiro’s crisis continues. He uses multiple forms of the Water Breathing technique to hold out against Yahaba’s final Blood Demon Art, the "Kouketsu Arrow." Meanwhile, Nezuko and Susamaru are still battling it out. Worried about the outcome, Tamayo unleashes her own Blood Demon Art.

Tanjiro's next destination, according to his Kasugai Crow, is to the south-southeast. On the way, Tanjiro runs into his fellow Final Selection survivor, the swordsman Zenitsu Agatsuma. Tanjiro has a hard time dealing with Zenitsu's passive attitude as they head deep into the mountains. They encounter two children whose older brother was taken away right in front of their house. There, Zenitsu hears the sound of a tsuzumi ringing out from somewhere.

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.

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.

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...

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...

Tanjiro's group, fresh from completing their training at the Butterfly Mansion, head to their next mission, the Mugen Train. There they rendezvous with Rengoku, who arrived ahead of them. Tanjiro is overwhelmed by the always-energetic Rengoku, Zenitsu is frightened by the prospect of facing demons as usual, and Inosuke is immensely excited by the sight of the huge machine. But on this train loaded with passengers, a new battle is about to begin.

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 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.

Enraged by Daki's contempt for human life, Tanjiro attacks her with more intensity and gradually corners the demon. But he's already gone past his physical limit. As Tanjiro collapses and all seems lost again, Nezuko appears. A vicious battle ensues and Nezuko starts transforming into a more demon-like form...

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.

Tanjiro, Zenitsu and Inosuke have joined Uzui in battle. While Zenitsu and Inosuke take on Daki, Tanjiro and Uzui deal with Gyutaro; however, they struggle as the demons have the upper hand with their coordinated attacks. But thanks to Hinatsuru's help and some teamwork from Uzui, Tanjiro's blade finds its way towards Gyutaro's neck...

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.

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.

Genya aims for the neck of the fifth demon that split off from Hantengu, but the demon's neck is shockingly hard, and his sword snaps in half in his attempt to strike it. His gun is also ineffective and Genya is driven into a corner. Realizing that he is unable to sever the neck by himself, he entrusts defeating the fifth demon, which is believed to be the main body, to Tanjiro. Taking on Genya's will, Tanjiro wields his sword against the fleeing demon...

Tanjiro, Nezuko, and Genya are struggling through an arduous battle against Zohakuten and his five tree dragons. They are forced to fight defensively against the tree dragons using the four emotion demon's powers, and Tanjiro is swallowed by one of them amidst the fight. Just as Tanjiro is close to meeting his demise, Mitsuri arrives in the nick of time and rescues him. And now, Mitsuri faces off against Zohakuten to rescue the captured Nezuko and Genya...!

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.