After the Mugen Train incident, Akaza visits Muzan Kibutsuji. Guided by a crow, Tanjiro Kamado heads off to the Rengoku residence to convey Kyojuro Rengoku's last messages to his father and little brother. Tanjiro's group return to the Butterfly Mansion.
Remembering Kyojuro Rengoku's battle with Akaza and recalling his final words, Tanjiro begins to cry for his esteemed friend. Zenitsu and Inosuke too burst into tears, Inosuke himself fighting hard and yelling that they would continue to train, while Kakushi arrive to assist them. Kyojuro's own Kasugai crow reports his death to the Rengoku residence, where his brother Senjuro is informed of the incident, causing him to fall to the floor in tears. Another Kasugai crow reports to the Demon Slayer Corps, where Kagaya Ubuyashiki is told of Tanjiro's furious confrontation with Upper Three.
Elsewhere, a family talks about their adopted son Toshikuni, praising him for his intelligence and kind nature. The boy, having burrowed a botany book from the library, begins to read it for a certain plant. Suddenly, the room's curtains shake open and Akaza appears, reporting to Toshikuni, in actuality a disguised Muzan Kibutsuji. As his blue eyes turn back into their demonic plum red, Muzan hears Akaza's report of his inability to find the Blue Spider Lily. Akaza also adds that he had killed a Hashira.
Infuriated, Muzan takes hold Akaza's cells and causes him to decay and bleed heavily. As Akaza fights the pain, Muzan angrily accosts him for boasting he had killed a Hashira. Since to him it is logical for demons to kill humans, he asks why he feels so proud when three other demon slayers were also present and could have been killed as well. Disappointed, he dismisses Akaza for his failure, mocking him for taking a blow from a non-Hashira swordsman. Alone in a forest, Akaza hurls Tanjiro's Nichirin sword into a nearby tree. Remembering Tanjiro had called him a coward, Akaza furiously punches the sword into pieces, before declaring he would spill his brains the next time they meet, now able to recognise his face.
In the Butterfly Mansion, Zenitsu ponders on their situation; he is stunned to think Kyojuro's death brought even the optimistic Tanjiro to despair and hopelessness and had caused the hardened and brash Inosuke to bawl his eyes out. Having stolen some bean buns from Aoi, he tries to give one to Tanjiro, only to bump into a shakened and hysterical Kiyo. She fearfully worries for Tanjiro, who had continued to train despite not recovering fully and is now nowhere to be found. Tanjiro, who had been following Kyojuro's Kasugai crow, arrives at the Rengoku residence. He then sees Senjuro Kyojuro, with a saddened expression from hearing of his brother's passing. Tanjiro arrives to relay him Kyojuro's message, only to hear a drunken Shinjuro Rengoku accuse the message to be worthless. He rants that Kyojuro's worthlessness and lack of talent had gotten him killed, denouncing him as a fool of a son.
He angrily tells his remaining son to stop grieving his brother's death, as Senjuro fights hard to stop crying. Unable to believe what he's hearing, Tanjiro steps in and demands he stops insulting his late son. Shinjuro suddenly sees his earrings and angrily tells him he is a user of Sun Breathing. Not knowing what it is, Tanjiro is suddenly tackled to the floor by the former Flame Hashira, who hits away Senjuro for trying to stop the fight. Tanjiro breaks free of his hold, only for Shinjuro to angrily claim he had arrived to mock them as a Sun Breathing user. He explains Sun Breathing is the original and the most powerful breathing technique of all, the others styles had been mimics of it. When Shinjuro tells him not to get cocky for being a Sun Breating user, Tanjiro breaks down and asks if Shinjuro is unable to see his own weakness had caused him despair from being unable to save Kyojuro. As he sprints towards Shinjuro and readies a punch, the former Hashira grabs him and violently punches his face repeatedly, until Tanjiro headbutts him to stop.
Later, Tanjiro apologises to Senjuro for headbutting his father, but he is informed Shinjuro has already left to buy more sake. Senjuro thanks him for defending his late brother, as he believes himself unable to stand up for him. He presents Tanjiro with the records created by the past Flame Hashiras, only for both to be shocked seeing the pages ripped when they open it. Senjuro apologises, believing his father had torn the pages, though Tanjiro dismisses the apology, instead stating he would train harder and master his Hinokami Kagura. Tanjiro declares to Senjuro he will one day become a Hashira like Kyojuro, no matter what it takes. This causes Senjuro to cry, as his brother didn't have a Tsuguko and he himself is not a powerful swordsman, his Nichirin blade even was unable to change colour. As he sadly states he would cause the long line of generational Flame Hashira to break, he believes Kyojuro wouldn't have been upset.
Before Tanjiro departs, Senjuro tries to give him Kyojuro's tsuba. Tanjiro refuses, not wanting to be given such a valuable item, though Senjuro insists. Later that evening, Senjuro attempts to talk to his father about Kyojuro's final message to him. Shinjuro angrily dismisses him, calling it worthless and believing the message is something bad about him. Senjuro relays Kyojuro's message, "Please take care of yourself", before quietly leaving. Now by himself, Shinjuro sets his drink down and begins to mourn his son's death alone.
As he walks home, Tanjiro suddenly sees Hotaru Haganezuka, armed with two knives. Angered at him losing another one of his blades, he chases Tanjiro for an entire day, until Aoi rescues him and calms Hotaru down. For the next four months after Kyojuro's death, Tanjiro, Inosuke and Zenitsu continue to train together, in order to able to fight and slay demons once again. Later on, Tanjiro battles a spider-like demon, with Nezuko supporting him, since she is now recognised but the Demon Slayer Corps. They chase the demon out of a mountain temple and corner it into a shed, before defeating it.
Returning from his mission tired, Tanjiro hears a cry for help from Aoi. The Sound Hashira, Tengen Uzui, had arrived to the Butterfly Mansion and proceeds to forcefully kidnap both Aoi and Naho. As Kiyo and Sumi cry for their release, Kanao panics. Without Shinobu and seeing her superior abducting her friends, she tries to rationalise the situation with a coin toss to decide. Suddenly remembering Tanjiro's words to follow her heart, she unexpectedly stops Tengen in his tracks, attempting to pull Aoi and Naho free. Kiyo and Sumi assist her, though they do little more than inconvenience the far more powerful demon slayer. Tanjiro arrives and accosts Tengen for his actions, trying to headbutt him. Without warning, Tengen disappears and lands onto a nearby gate arch, while Tanjiro and Kanao help Kiyo and Sumi up.
Tengen tried to announce his title as a former Shinobi and that he is able to take them for his mission without Shinobu's permission. Upon learning Naho isn't a demon slayer, he promptly drops her, forcing Tanjiro to run in and catch her from falling. Angered at his actions, Tanjiro refuses to acknowledge him as a Hashira, infuriating Tengen, who believes their "unflashiness" is why the Demon Slayer Corps is getting weaker. Tanjiro, still attempting to free Aoi, declares that "we" would accompany Tengen for his mission. Not knowing who "we" is, he is answered by the sudden appearance of both Zenitsu and Inosuke. Together, they announce they will join him. Satisfied he has the three to accompany him, Tengen warns them not to defy him again, before slapping Aoi from behind.
As they leave the Butterfly Mansion, the three stand behind Tengen, waiting for orders. As Zenitsu marvels as his immense stature, Inosuke impatiently asks where they will be going. Tengen answers, "The number-one spot in Japan that's dripping with lust and desire. A super-flashy place. The Entertainment District, where demons reside".
Characters in Order of Appearance
- The anime added an extra scene in which Tanjiro fights a spider-like demon alongside Nezuko. It takes place shortly before Tengen arrives at the Butterfly Mansion.