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.

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.

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...

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.

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.

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...

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.

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...

The injured Tanjiro, Zenitsu and Inosuke are sent to the home of the Insect Hashira, Shinobu Kocho, for treatment. Two weeks later, Tanjiro and Inosuke start rehabilitation training. But the drills are brutal, and they find themselves broken in spirit. Unaware of the grueling regimen, Zenitsu joins them late and is visibly enthusiastic in front of girls, but...

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 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.

As Tanjiro close in on the demon that has been preying upon the entertainment district. But even as he closes in, the others continue to follow their leads toward their query. Who will find the demon first? And will they be able to survive the confrontation when they do?

After being told of Zenitsu’s disappearance and to leave the Entertainment District by Uzui, Tanjiro and Inosuke decide that they will rescue Zenitsu. That evening, Tanjiro picks up a scent of a demon, which leads him to Koinatsu Oiran being swallowed by Daki’s belt. With Uzui nowhere in sight, Tanjiro must face the Upper Six demon alone.

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 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.

An Upper Rank Demon has been defeated for the first time in a hundred years by Uzui, Tanjiro, and his comrades' effort. This news causes a ripple effect not only among the members of the Demon Slayer Corps, but also the Upper Rank Demons, who have been summoned by Muzan Kibutsuji. Meanwhile, Tanjiro is recovering at the Butterfly Mansion when he discovers that he has upset his swordsmith Haganezuka after chipping his sword and decides to head to the village where the swordsmiths live to talk to him in person.

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

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...

Armed with his memories, Muichiro feels powerful and invincible, convinced that the demonic fifth moon has no chance against him.