Demon Slayer - Season 3

After their battle with the Upper Rank Six siblings, Tanjiro, Zenitsu, Inosuke, and Nezuko are found by the Kakushi. In the Infinity Castle, Muzan Kibutsujisummons the remaining five Upper Rank demons – Akaza, Upper Five Gyokko, Upper Four Hantengu, Upper Two Doma and Upper One Kokushibo. He admonishes them for their failure to kill the Ubuyashikis and find the Blue Spider Lily. When Gyokko provides new information, he is sent on a joint mission with Hantengu. While Zenitsu and Inosuke are summoned to individual missions, Tanjiro continues his rehabilitation. When his swordsmith Hotaru Haganezuka refuses to forge him a new sword, Tanjiro is told to meet him at the Swordsmith Village to discuss the matter in person. He arrives with Nezuko and meets the village's chief, Tecchin Tecchikawahara, who reassures Tanjiro he will bring Hotaru back to build the sword. Tanjiro is later shown to the village's hot springs where he meets the Love Hashira Mitsuri Kanroji, who is initially dejected after being ignored by an unknown person. While in the hot springs, Tanjiro encounters Genya, the Wind Hashira Sanemi Shinazugawa's younger brother and fellow Demon Slayer, who refuses Tanjiro's hospitality and storms off. At the village, Mitsuri hints at Tanjiro about a "secret weapon" hidden somewhere that can make him stronger and bids farewell to the siblings. The next day, while searching for the weapon, Tanjiro finds the Mist Hashira Muichiro Tokito in an argument with someone and sees that seemingly with them is a man from his dreams.

While eavesdropping, Tanjiro watches as Muichiro threatens the swordsmith he was arguing with. He tries to defend him but the indifferent Hashira knocks him out for interfering. After waking up, the boy, named Kotetsu, explains that the "man" he saw is actually an advanced mechanical training doll, built after a swordsman who lived over 300 years ago. He explains the doll was made by his ancestors, and as he lacks a family, it is all he has to pass on to the next generation. Tanjiro agrees to protect it, but Muichiro appears, having finished his training session and causing extensive damage. However, after Kotetsu discovers it is still functional, he tells Tanjiro to train with it in order to become stronger than the arrogant Muichiro. However, training proves harsh as Kotetsu denies Tanjiro food and water when he fails to connect hits on the doll. When Tanjiro eventually faints from exhaustion, he imagines himself in the afterlife and sees a peculiar stone in the Sanzu River, enabling him to detect a scent faster than the Opening Thread. He uses this to his advantage, eventually landing a powerful strike on the doll's head, which shatters and reveals a concealed sword inside.

Tanjiro becomes disappointed after he discovers the sword rusted. However, a swole Hagenazuka appears, revealing he trained in solitude to be able to forge a better sword for Tanjiro. As such, he offers to restore the rusty sword, giving Tanjiro another one in the meantime. That night, while trying to befriend Genya, swordsmith Kanamori is brutally devoured by Gyokko who, alongside Hantengu, has found the village. After Muichiro is moved by Tanjiro's sense of kindness towards others, Hantengu enters their room, only to be quickly beheaded. However, two individual demons regenerate from the severed body parts, each with different, powerful abilities. After one of them blasts Muichiro far away, the other nearly electrocutes Tanjiro with a staff, before Genya appears and beheads them both with a sawed-off shotgun and a Nichirin knife. However, Hantengu again duplicates, and one of the demons deafens Tanjiro with a sonic attack while Nezuko tries to defend Genya. Meanwhile, Muichiro runs back to assist, but finds Kotetsu in peril from one of Gyokko's spawn. Initially electing not to help him, he saves him just before being eaten after remembering about the importance of kindness with others.

Muichiro rescues Kotetsu who is being attacked by a goldfish demon; Nezuko and Genya face off against demons; Separated from the others, Tanjiro fights a battle with a demon marked with the word 'Joy'.

Upon arriving, Mitsuri comes to Tecchin, the chief of the village, and finds out all of his guards have been defeated.

Muichiro is trapped in water by Gyokko's Blood Demon Art. Tanjiro and and his comrades have successfully severed the necks off the four demons, but they realize that they cannot be defeated this way.

As Tanjiro was just about to sever the neck of the fifth demon, another demon approaches from behind him. This demon turns out to be Zohakuten, a demon created by combining all four Emotion Demons into one body, marked with the word "Hatred." Tanjiro makes a narrow escape from the attack and fails to sever the neck of the fifth demon. After hearing Zohakuten calling him and his comrades "awful villains" for trying to sever the neck of the cowering demon, Tanjiro is enraged and decides to face him...

With Kotetsu's help, Muichiro finally manages to escape from Gyokko's Blood Demon Art, but he is close to reaching his limit with all of the damage he has sustained. As the goldfish demons draw closer to the battered Muichiro and Kotetsu, Muichiro's memory is awakened the very moment the demons attack. In this memory, he remembers his father, a lumberman, his mother, and his older twin brother, Yuichiro...

After defeating the goldfish demons, Muichiro heads to the studio where Haganezuka and Kanamori are. There, in order to disrupt Haganezuka's focus on whetting the sword, Gyokko was attempting to take Kanamori for hostage. Muichiro arrives in the nick of time, receives the Nichirin Sword from Kanamori, and challenges Gyokko once again...

After rescuing Tanjiro who was swallowed by one of the tree dragons, Mitsuri now faces off against Zohakuten in order to save Nezuko and Genya. Mitsuri skillfully fends off the fierce attacks from the tree dragons, but she is struck with a powerful attack from Zohakuten and loses consciousness right before she is able to land a decisive blow. As a killer blow is about to strike down on her, Mitsuri recalls a memory of her past self and her special constitution...

As Mitsuri holds off Zohakuten, Tanjiro, Nezuko and Genya use this time to chase after Hantengu's main body. The three manage to find the tree ball that Hantengu is hiding in, but when they slice it open, they find that it is completely empty. Hantengu makes a run for it again, and Tanjiro and the others continue chasing him. Seeing Hantengu running about, Genya snaps and hurls a tree at him, and Nezuko jumps at him!