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...