Upper Ranks Meeting

The Upper Ranks Meeting was a gathering that immediately followed the deaths of Upper Rank Six demons Daki and Gyutaro. It occurred in the Infinity Castle and concerned Muzan Kibutsuji's growing disappointment and lack of faith in the Twelve Kizuki's remaining Upper Ranks, and their inability to do as he ordered and succeed.

Prologue
For 113 years, the Upper Ranks of the Twelve Kizuki have only been the ones to successfully kill members of the Hashira, the strongest swordsmen of the Demon Slayer Corps. On the other hand, Muzan had grown tired of the Lower Ranks' lack of success and its demons continuing to fail and live up to his expectations. Moreover, whilst the Upper Ranks have stayed the same for more than a century, the Lowers continue to shift and change position due to their frequent deaths. The death of Lower Five, Rui, at the hands of the Demon Slayers was eventually the final straw. No longer believing it to be worthwhile to have their positions maintained, Muzan ordered Nakime, the Biwa Demon, to summon the five remaining demons to the Infinity Castle in order for him to kill them all. Amongst them, only one, Lower One Enmu, was spared, due to his willingness to please Muzan and was rewarded with ample blood to strengthen him.

Muzan ordered Enmu to kill a Hashira and he tried to do so with a complex plan; using an entire train that had been reported to have many victims vanish inside it, he assimilated his body with the train and waited for the intervention by the Demon Slayer Corps. Eventually, the Flame Hashira, Kyojuro Rengoku, was tasked with its investigation, and he was accompanied by the Demon Slayers Tanjiro Kamado, Zenitsu Agatsuma, Inosuke Hashibira, and the rogue demon Nezuko Kamado. Although Enmu had successfully lured them all into his sleep-based Blood Demon Art, Tanjiro's strong spirit and resolve allowed him to break free and confront Enmu. Soon re-joined by the rest of the team, Tanjiro and Inosuke were able to successfully kill Enmu after a lengthy battle, leaving Lower One to lament his inability to kill even a single person.

Not long after the battle came Upper Rank Three Akaza, who was tasked with finding the Blue Spider Lily. Finding the train wreckage and seeing the Demon Slayers, he saw Kyojuro as a worthy warrior to become a demon and attempted to kill the still injured Tanjiro out of spite. Kyojuro stopped his attack and confronted the new demon. Seeing that he is unwilling to turn, Akaza engaged the Flame Hashira in a fierce battle that ended in his escape and Kyojuro's death.

Akaza reported his findings to Muzan, who became angered at his failure to find the lily and his inability to kill the other Demon Slayers, punishing the Upper Rank by causing his cells to decay as torture. Disappointed, he dismisses Upper Three for shamefully getting hit by a non-Hashira Demon Slayer, leading Akaza to channel his anger towards Tanjiro. Four months later, the Sound Hashira, Tengen Uzui, was tasked with investigating a demonic presence within the red-light district of Yoshiwara. Through a lengthy investigation involving his wives, Tanjiro, Zenitsu, and Inosuke and following a destructive and lengthy battle that left most of the city in ruins, the demon siblings Daki and Gyutaro, dual holders of Upper Six of the Twelve Kizuki, were defeated.

Meeting
Following the deaths of the siblings, Akaza suddenly finds himself inside the Infinity Castle. Initially confused, he immediately realizes that an Upper Rank was killed to cause him to appear in the fortress. Travelling across the Infinity Castle, passing through a large palace, shifting lower rooms, and a pillar-riddled maze, he eventually is taken before Nakime. Upper Rank Five Gyokko greets Akaza cordially, though the tattooed demon ignores his attempts at a conversation.

Gyokko wonders if it has been 90 years since they have last seen each other, only for Hantengu, Upper Rank Four, to correct him and state that it has actually been 113 years since the last summoning of the Upper Ranks. Akaza questions Nakime on Muzan's whereabouts, to which the Biwa Demon answers that the Demon Progenitor has not arrived. When he asks on the location of Upper Rank One, he is interrupted by Doma, Upper Rank Two. Doma wonders if Akaza had given him any thought, as he had worried about the safety of his fellow Upper Ranks over the last century. Gyokko greets Doma cheerfully, who then thanks him for the lovely vase he was gifted, adding that it sits in his room with a woman's severed head on it. Akaza demands that Doma lift his arm off of him and immediately breaks off his lower jaw with a punch. Though Hantengu is frightened by the violence, Doma instantly heals and compliments his "friend" on whether he had got stronger, angering Akaza with his callous attitude. Nakime then calls out that Upper Rank One has been present the entire time; Akaza looks to the edge of the platform and sees Kokushibo, who calmly sits in the distance and announces the arrival of their master. Muzan appears before them all, standing upside down due to the castle's unusual gravity. As he calmly mixes different chemicals into a chemistry set, he addresses the death of Gyutaro, expressing his disappointment in his ability to kill the Demon Slayers sent to kill him. To this, Doma apologizes on his behalf as it was he who had introduced the demon to the Twelve Kizuki. Happily asking whether he should be punished, he offers to gouge his own eyeball as penance. Muzan ignores his offer and instead claims that Daki was a hindrance; had Gyutaro simply poisoned the Demon Slayers and left, he could have succeeded. He denounces the Upper Ranks by claiming they are no longer ranked by power anymore but by their remaining humanity, citing Gyutaro's love and care for Daki as an example. Doma, in his attempt to placate his master, tries to ask if he had ever failed him. Muzan cites their failures as the Ubuyashiki family remaining alive and the Blue Spider Lily still not found, before angrily stating that he is now unsure why they are still existing. Hearing this, Hantengu grows fearful and begs Muzan for forgiveness, Akaza remains silent knowing his recent failure, Kokushibo humbly accept his inability to find the Ubuyashikis and Doma apologizes for his lesser skill in detective work.

Gyokko suddenly speaks up and claims that he has information to present. He then appears in Muzan's hand as a severed head, having been decapitated instantly without the Upper Rank realizing. Taking the head, Muzan reads Gyokko's mind for his provided information, while speaking of his detest towards change in any form, be it in situation, body, or emotion. To this, Gyokko agrees and claims that he too prefers the unchanging, permanence. Muzan, enraged at the first change in the Upper Ranks in 113 years, demands that Gyokko never present his information without confirming it, before dropping the demon's head. Muzan orders the Upper Ranks to all exert and push themselves with greater desperation, believing he has been too lenient with them being his most powerful demons. He informs Gyokko that Hantengu will be joining him on his mission once the information is confirmed, before doors summoned by Nakime close on Muzan, ending the meeting.

Aftermath
Hantengu complies with Muzan's command. Gyokko, annoyed that another demon will join him in a mission he had provided, nonetheless obeys, albeit begrudgingly. Doma, wanting to join in, attempts to ask Gyokko on what kind of information he had given Muzan. Gyokko attempts to ignore him, believing the information is secretive. When Doma asks again, Akaza appears behind him and punches off the top of Upper Two's head, angered that Doma is attempting to join a mission without Muzan's orders. Immediately after this, Akaza's hand suddenly falls off. Kokushibo instantly appears and confronts Upper Three, stating that he has gone too far. Doma, healing the massive wound without issue, tries to placate Kokushibo, but he only informs Doma that he is not punishing Akaza for his sake. Instead, he is disturbed that Akaza would attempt to disrupt the hierarchy of the Upper Ranks, as his disruptive actions undermines subordination.

The ancient swordsman tells Akaza to request a blood battle should he feel the need to replace them, only for Doma to shoot down the idea, claiming that Akaza would never be able to beat either one of them. Doma adds that Akaza is simply angry at him for surpassing his rank in a shorter amount of time, earning Akaza's ire. Upper Two attempts to defend Upper Three's actions by stating that he had not dodged on purpose, claiming it is their way of bonding. He states that as the two highest ranked members, they must be lenient to those below him. Instead, Kokushibo directly asks Akaza if he had understood what he has said. The enraged demon acknowledges his message, before threatening to kill him. Upper One gives his encouragement and vanishes from view, with Akaza and Doma bidding the demonic swordsman goodbye. Doma comments on feeling left out of their conversation, only for Akaza to leave the Infinity Castle at that moment, ignoring Doma's attempts to talk to him. Gyokko then calls out to Nakime and instructs her to take him and Hantengu to the location he was assigned with. With a strum of her biwa, Upper Five and Upper Four disappear from the castle. Doma, now alone, attempts to talk to Nakime, only to be declined and transported back to his room, leading him to comment about his fellow demons' cold, indifferent attitudes.