It’s the Taisho period in Japan.

Tanjiro, a kind boy who sells charcoal for a living, suddenly loses all of his family members; they are killed by a Demon.

Moreover, the only survivor, Nezuko, Tanjiro’s little sister, has been transformed into a Demon.

Although Tanjiro is devastated by the cruel reality,
he decides to pursue the path of “Demon Hunting” to turn his sister back into a human,
and avenge the Demon who killed his family.

“Group strength training starts now!”

The Demon Slayer Corps successfully defended the Swordsmith Village from the demon attack,
destroying Upper Four and Upper Five. Following their desperate struggle in the village,
a special mark manifested on two Hashira—Muichiro Tokito and Mitsuri Kanroji.

Consequently, the “manifestation of the Marks on the Hashira”
became an urgent necessity in order to defeat Muzan Kibutsuji.

Furthermore, to strengthen the entire Demon Slayer Corps from the bottom up,
the decision was made to implement the first group strength training,
“Hashira Training,” proposed by Stone Hashira, Gyomei Himejima, at the Hashira Meeting. Tanjiro and the other Demon-Slayer swordsmen each visited the Hashira,
focusing on their training with all their hearts and souls.

Meanwhile, Muzan, in order to obtain Nezuko, had personally appeared at the Ubuyashiki Mansion.

“...Hello. You came. It is our first meeting... Muzan... Kibutsuji...”

“You are... in an unsightly condition... Ubuyashiki...”

At the end of a continuous thousand-year fate, Kagaya and Muzan now face each other. And then—

“EMERGENCY SUMMONS!! EMERGENCY SUMMONS!!
AN ATTACK ON UBUYASHIKI MANSION! AN ATTACK ON UBUYASHIKI MANSION!!”

The sudden news throws the Demon Slayer Corps into an uproar.

“To the Master’s side, immediately!” the Hashira and Tanjiro dash toward the Ubuyashiki Mansion,
but along with the entire Demon Slayer Corps, they are thrown by Muzan into his stronghold, the Infinity Castle.

What on earth is happening?

Insect Hashira, Shinobu Kocho, encounters Upper Two, Doma, who wears an eerie smile.

Elsewhere, Kaigaku, who has become Upper Six, appears.

Facing his former senior disciple, Zenitsu Agatsuma lets his emotions explode.

A cruel, blood-soaked, long, long night has begun.