Plot
In the Demon Slayer Corps' Swordsmith Village, Tanjiro Kamado, his demon sister Nezuko, and Demon Slayer Genya Shinazugawa assist Love Hashira Mitsuri Kanroji against Upper Rank Four Hantengu, who has hidden himself while his manifested hatred Zohakuten attacks them.[8] In the midst of battle, Mitsuri awakens a mysterious mark that greatly enhances her strength and speed, forcing him to focus on her and allowing the three to pursue Hantengu. Tanjiro uses his Hinokami Kagura to slash his neck, but Hantengu summons his manifested resentment Urami.
Urami attacks Genya and Tanjiro until Nezuko burns him with her Blood Demon Art. They fall down a cliff when Mist Hashira Muichiro Tokito and swordsmiths Kozo Kanamori, Kotetsu, and Hotaru Haganezuka arrive to support them. With his last strength, Muichiro gives Tanjiro Hotaru's unfinished sword. He beheads Urami but Nezuko begins to burn as dawn breaks. Panicking, Tanjiro then sees that Urami's beheaded body is still moving because Hantengu is not dead.
Tanjiro freezes in his indecision until Nezuko signals him to kill the demon. He finds Hantengu hiding in Urami's heart and exposes him to sunlight after slicing Urami in half. Hantengu remembers his human past as Tanjiro kills him, saving Mitsuri as well when Zohakuten disintegrates. Tanjiro mourns Nezuko's death but she is revealed to be alive, no longer burning, and has regained the ability to speak slightly.
Through Hantengu's memories, Muzan Kibutsuji learns of Nezuko's new immunity, realizing his goal to be immortal will be fulfilled if he devours her. In the aftermath of the battle, Muichiro thanks Tanjiro for helping him to regain his identity, Mitsuri embraces them for all for surviving, and the village celebrate the siblings for their victory.
In another mission, Serpent Hashira Obanai Iguro and Wind Hashira Sanemi Shinazugawa investigate an abandoned temple inhabited by demons. They discover it is one of several portals to the Infinity Castle, a vast extra-dimensional space that serves as Muzan's lair. While his friends Zenitsu and Inosuke return from their missions, Tanjiro recovers from his wounds; Hotaru gives him a new sword with the late Flame Hashira Kyojuro Rengoku's tsuba on it.
The Corps' leader Kagaya Ubuyashiki has become bedridden, and his wife Amane summons the Hashira to a meeting in his stead. Muichiro and Mitsuri inform them about the awakening of their marks, both of which happened under extreme duress. To ensure the others can attain theirs as well, they must undergo a special training regimen and submit the Corps to it, in order to prepare everyone for Muzan's arrival for Nezuko. However, Water Hashira Giyu Tomioka refuses to participate and leaves. Elsewhere, the demon Tamayo is visited by a Kasugai crow on Kagaya's behalf, asking her to join forces with the Corps.
