Twelve Kizuki

The Twelve Kizuki is an organization of the twelve most powerful demons in existence who are under the direct command of the Demon King, Muzan Kibutsuji. They also serve as the main antagonistic faction of Demon Slayer: Kimetsu no Yaiba.

Overview
The Twelve Kizuki is an organization of the 12 strongest beings amongst demon-kind, second in strength and authority only to the Demon King himself, Muzan Kibutsuji. Each member of the Twelve Kizuki has received a large portion of Muzan's blood, greater than any other demon, thus exponentially increasing their power. As a testament to this, every member of the Twelve Kizuki can use Blood Demon Arts, supernatural powers and techniques manifested through their blood that only significantly powerful demons have access to.

The Twelve Kizuki are divided into two groups, the six Upper Ranks, numbered one through six, and the six Lower Ranks, also numbered one through six. The number signifies their ranking among the Twelve Kizuki, determined by each member's level of strength, Upper Rank One being the strongest and Lower Rank Six being the weakest. The Lower Ranks have their numbers and ranks engraved only into one eye, whereas the Upper Ranks have their numbers in one eye and the kanji for "Upper Rank" in the other.

While the exact relationships between the two groups are unclear, it is known that the Upper Ranks despise the Lower Ranks.

The Upper Ranks each possesses a level of power that far surpasses that of the Lower Ranks; as proof of their strength, the strongest of the Demon Slayer Corps, the Hashira, have killed numerous Lower Ranks over the years, while the Upper Ranks have killed and eaten many Hashira. Kagaya Ubuyashiki states that it had been a hundred years since an Upper Rank has been killed following the defeat of Gyutaro and Daki. Furthermore, it has been remarked by Shinobu Kocho that the strength of an Upper Rank demon is, at least, comparable to three Hashira, although it should be noted that the capabilities of a Hashira vary from one to another, especially the ones who can manifest their Demon Slayer Mark to further augment their strength. While the Lower Ranks have been replaced countless times, the Upper Ranks did not change over 100 years at all.

When a member of the group is removed from the Twelve Kizuki, Muzan Kibutsuji demotes these members by slashing the pupils where the number signifying their rank is located, creating an "X" shaped scar over the digit, signifying that they are no longer part of the Twelve Kizuki. The only example of this happening is Kyogai, who had already reached his "limit" and could no longer consume human flesh. This gradually led to Kyogai losing his appetite for humans and beginning to lose the ability to evolve and become stronger. Therefore, he was deemed too weak to remain in his position of Lower Rank Six and subsequently removed.

After their most recent failure with the death of Rui, holder of Lower Rank Five, Muzan decided to dismantle the Lower Ranks completely. He ordered Nakime to summon each member to the Infinity Castle and proceeded to kill all of the Lower Ranks, sparing only Enmu, Lower Rank One, and giving him a chance to redeem himself by killing a Hashira and bringing him the head of Tanjiro Kamado. With Enmu's death at the hands of Tanjiro, the Lower Ranks are functionally disbanded with all of their members dead, and with Nakime's death at the hands of Muzan himself, the Upper Ranks are also functionally disbanded with all their members dead.

Mission
The Twelve Kizuki have been given three tasks to complete by Muzan's command:


 * To find the Blue Spider Lily (the key ingredient of the experimental medicine that made Muzan a demon), but since Muzan's discovery (via Hantengu) that Nezuko Kamado is immune to the sun, he has decided that the Upper Ranks' first focus is to capture her and bring her to him.
 * The destruction of the Demon Slayer Corps. As part of their Mission to destroy the Corps, Muzan gave the Twelve Kizuki specific orders to hunt down and eliminate the Ubuyashiki Family, as they are the Corps’s leaders and backers, and are ultimately what keeps the Corps alive and enables them to rebuild the organization again and again no matter how many times Muzan and the Twelve Kizuki try to destroy it.
 * After hundreds of years of failing at these two tasks, Muzan has decided that the Twelve Kizuki should serve him with suicidal devotion to ensure success.

Blood Battle
According to Kokushibo, if there is any dissatisfaction between the say members of the Upper Rank demons, the lower ranked challenger must invoke the right to kill or defeat their desired target in order to change their position in the hierarchy. Any that defies the rules will face retribution, as seen when Akaza attacked Doma who was a higher rank than him--the former had his arm sliced off by Kokushibo as a warning for disregarding the hierarchical order.

Privileges
As the Twelve Kizuki are deemed by Muzan to be the twelve most powerful demons (second only to himself), he is known to constantly give favor and special attention to all twelve members of the group. As seen when he would give several of the group's members special privileges normally not given to average demons. One of these privileges is that he would empower all members of the group with huge amounts of his blood in order to increase their power and strength in acknowledgement of their achievements and further strengthen them in order to be of further use in his plans.

Moreover, Upper Rank demons have the authority to transform humans they view as worthy into demons by giving them blood, and upon receiving permission from Muzan, their blood will transform into his'. This is seen with Gyutaro's and Daki's case where Doma was able to turn the siblings into demons by giving them his blood. This is also seen with Kaigaku, where Kokushibo was also able to turn the Demon Slayer into a demon by giving him his blood.

As seen from the case with Rui, Muzan himself had given him special permission to form a large group of demons — despite his own law of forbidding them to team up together in large numbers — in order to satisfy his longing for a family. Showcasing that despite his paranoia of the possibility of other demons teaming up together in order to overthrow him, his favouritism for Rui exempted him from immediately executing him and his new "family" and allowing its existence.

Furthermore, Muzan was shown to have given Gyutaro and Daki the special privilege of sharing the position of Upper Rank Six. His favouritism towards Daki's older brother, Gyutaro, allowed her to also have the rank and share it with him despite her being notably weaker than him and the other Upper Ranks.

In the case of Akaza, he was given special permission by Muzan to not eat women. Akaza was noted by Doma to have an unusual aversion to eating or even hurting women despite the immense power he could gain by devouring them due to their stronger nutritional value to a demon's development. Despite his orders for all Twelve Members of the Group to continuously strive for more power by eating humans in mass to be of better use to him, Muzan actually gave Akaza special permission to not eat women and indulged his unusual quirk due to considering him to be one of his favorite Upper Ranks. Akaza was also noted to be only deployed by Muzan for special assignments and nothing else, further showing the favor he gives him as one of his favorites.

List of Known Members
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History
The first of the Twelve Kizuki that was encountered in the series was the former Lower Rank Six, Kyogai, who is slain in battle by Tanjiro Kamado. Tanjiro and his companions would shortly thereafter embark on the Natagumo Mountains to face-off against Lower Rank Five, Rui, who was manipulating a group of demons to forcibly act as his family and to assist him in the killing of Demon Slayers. Tanjiro almost managed to behead Rui, but the demon outwitted him by using his threads to cut off his head. He is later saved by the timely arrival of the Water Hashira, Giyu Tomioka, who swiftly beheads Rui for good. Rui's death would later prompt Muzan Kibutsuji to lose his entire faith in the faction's ability and proceeded to dismantle the remaining Lower Ranks by coldly annihilating all members except for Lower Rank One, Enmu.

Enmu is then given an additional injection of Muzan's blood and tasked with killing the Hashira and Tanjiro as a last chance offer to save his life, with the promise of even more blood if he were to complete his mission. Enmu later intercepted Tanjiro with his companions on the Mugen Train. He planned to feast on the 200+ passengers by merging his body with the train and using his Blood Demon Art to trap them in their dreams. Through the joint effort of Tanjiro Kamado and Inosuke Hashibira, Enmu is soundly defeated, only for their short-lived victory to be interrupted by the unexpected arrival of Upper Rank 3, Akaza. Akaza would commence battle with the Flame Hashira, Kyojuro Rengoku. After a lengthy battle, Akaza mortally wounds Kyojuro but is forced to flee from the rising sun.

Daki, Upper Rank Six, is the next high ranked demon encountered. After receiving word of a demon claiming its feeding ground in the Entertainment District, Tengen Uzui (Sound Hashira) sets off with the aid of Tanjiro, Nezuko, Inosuke, and Zenitsu Agatsuma. The group manages to locate Daki and slice her neck off, only for her to reveal her older brother and the true Upper Rank Six, Gyutaro. Gyutaro and Daki, are then revealed to be sharing bodies and were finally both defeated after their simultaneous beheading.

Immediately following the deaths of Gyutaro and Daki (Upper Rank Six), Muzan summoned the remaining members of the Upper Ranks and gave Hantengu and Gyokko (Upper Rank Four & Five, respectively) a mission to exterminate the Swordsmith Village, to reduce the power of the Demon Slayer Corps by removing their ability to fight on par with the demons without Nichirin Sword. Both Hantengu and Gyokko were slain, but not before Hantengu witnessed (before dying) Nezuko standing in the sun and telling Muzan. This shifted Muzan's main interest in devouring Nezuko to conquer the sun.

After his attack on the Ubuyashiki Manor, Muzan escaped into the Infinity Castle thanks to Nakime. It's revealed that Nakime has replaced Hantengu as the new Upper Rank Four and that Kaigaku (a former Demon Slayer and senior to Zenitsu Agatsuma) became the new Upper Rank Six after an encounter with Kokushibo, thereby replacing Gyutaro and Daki. It is unknown who the new Upper-Rank Five was, or if Muzan was even able to find a replacement in the first place.

Shortly after arriving in the Infinity Castle, Shinobu Kocho would stumble upon Upper Rank Two, Doma, feasting on his female cult followers in his chamber. A single woman survived, only to be mercilessly mutilated by Doma despite Shinobu's hasty efforts to save her. The battle commenced between the Hashira and Upper Rank. However, Shinobu's assortment of poison proved to be useless against Doma's might. The demon would then proceed to promptly defeat and absorb the Hashira, only for Kanao Tsuyuri to arrive just too late to save her.

Zenitsu later ran into Kaigaku and had a duel to the death with his former classmate, resulting in Kaigaku's death and Zenitsu almost dying. Elsewhere in the castle, Tanjiro and Giyu Tomioka are located by Akaza. Akaza proved to be a fearsome opponent, nearly killing the two. Even after having cut off his head, Akaza through sheer willpower was able to keep his body from fading. Only through memories of his previous life and name as a human (Hakuji) and seeing visions of important figures of his past did he finally give in and pass on.

Doma continues his fight against Kanao, who is unexpectedly assisted by Inosuke Hashibira. He initially overwhelms the two with his cryokinetic Blood Demon Art, but was unexpectedly weakened by the lingering effects of Shinobu's wisteria flower poison after having absorbed her body. The two through their combined efforts were then able to sever Doma's head, putting an end to Upper Rank Two.

The Love Hashira, Mitsuri Kanroji and Serpent Hashira, Obanai Iguro confront the newly appointed Upper Rank Four, Nakime. The demoness outwitted the pairs' attempts by the usage of her Blood Demon Art that warps and controls the entire infrastructure of the Infinity Castle as she sees fit. Simultaneously, the Mist Hashira, Muichiro Tokito was separated from the Stone Hashira, Gyomei Himejima by Nakime's Blood Demon Art, falling into the location of the most powerful Upper Rank demon, Upper Rank One, Kokushibo.

Kokushibo instinctively sensed the blood relation between him and Muichiro. Impressed by Muichiro's proficiency with his Breathing Style, Kokushibo unsheathed his sword and revealed his Moon Breathing form. The attack would sever Muichiro's left arm and he is swiftly defeated with minimal effort. Instead of killing the boy, Kokushibo decides that he will transform Muichiro into a demon due to sentimentality in their blood relation and respect for his fighting ability. Genya Shinazugawa, waiting for an opportunity to ambush Kokushibo from behind, fires off his shotgun in an attempt to save Muichiro. Faster than Genya can follow with his eyes, Kokushibo immediately dismantles him; both arms are sliced off and he is bifurcated at his waist. Kokushibo mentions having encountered a Demon Slayer with a very similar physiology about 300 years ago, and prepares to kill Genya via decapitation. Before he could administer the final blow, Genya is saved by the timely arrival of his older brother and Wind Hashira, Sanemi Shinazugawa.

Sanemi manages to exchange blows against Kokushibo, albeit only for a short moment. After receiving a brutal injury from an attack, Sanemi reveals that he has "Marechi blood". He intended to use the intoxication effects of his premium blood as a distraction when fighting, and while Kokushibo is momentarily caught off guard by the scent, it has little to no effect thereafter. Using everything he could manage to think of and at his wit's end, Sanemi is almost killed by a barrage of blade swings. The Hashira is saved by the intervention of his comrade, Gyomei Himejima, the Stone Hashira and strongest Demon Slayer in the Demon Slayer Corps.

A difficult battle ensues between the Upper Rank One and the Hashira with the demon exploiting his extraordinary eyesight abilities along with his blades made of flesh. As he is pushed further into a corner, Kokushibo's blade grows far longer developing multiple smaller blades, further increasing both his already massive range and attack power, slowly overpowering the Hashira. A weakened but still alive Genya, manages to recover and remembering Tanjiro's words that being weaker gives him the unique advantage of being unnoticed by their enemies, uses the element of surprise to shoot demon bullets into Kokushibo who is immobilized and weakened by Muichiro's blade thrust into the demon's abdomen along, the bullets growing trees inside Kokushibo, further depriving him of his movement and strength. He becomes increasingly desperate in his desire to win, and Gyomei seizes the chance to smash his head into the ground. This does not end the Upper Rank who regrows his head and, increasingly desperate for victory, starts developing flesh blades on his own body and becomes far more aggressive and monstrous.

The demon, however, has an internal conflict after witnessing his ugly form through his reflection on Sanemi's blade, and how what he has become contrasts significantly with what he wanted to be. As his thoughts of seeking to avoid defeat and resentment towards his self heavily conflict with him, his body begins to decay, exactly at the point where Muichiro stabbed him, struggling for a final time, the Upper Rank One's body crumbles away, as he realizes that all he wanted was to be like his younger, more talented brother, signifying the end of the highest-ranking member of the Twelve Kizuki.

Obanai and Mitsuri are later shown to still have great difficulties with reaching Nakime's position; constantly being thwarted in their attempts by her Blood Demon Art throughout the entire duration of the Demon Slayer Corps' battles with the Upper Ranks. The two shortly thereafter are able to reconvene with Tanjiro and Giyu with the helpful assistance of the recently slain demoness doctor, Tamayo's assistant, Yushiro. Yushiro manages to ambush Nakime using his Blood Demon Art: Blindfold while she was distracted and assumes control of her body by altering her vision. Yushiro declares his intention of vengeance against Muzan for killing Tamayo; vowing to use his Upper Rank's ability against him to disassemble the castle and bring him to the light. Realizing the danger to himself, Muzan remotely detonated Nakime's head through his influence, killing her, although her body still remained active for sufficiently long time to bring the fortress into the surface. This attempt at self preservation effectively eradicated the Twelve Kizuki. Furthermore, following Muzan's own demise, terminated any chance for the organization to rebuild.