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...

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...