Twelve Kizuki

The Twelve Demon Moons are a group of twelve powerful Demons under Muzan Kibutsuji's command, who have all were given a portion of his blood which have augmented their powers.

Structure
The Twelve Demon Moons are divided into two groups, the Upper Moons and the Lower Moons. Each has their number engraved into their eye(s), with the Lower members having it in only one, whereas Upper members have it in both. This number signifies how strong the member is, with Upper Moon One being the strongest and Lower Moon Six being the weakest overall, and while the exact relationships between the two groups are unclear, it is said by Muzan himself that the Upper Moons despise the Lower Moons. When a member of the group is kicked out and removed from the Twelve Demons Moons, Muzan Kibutsuji demotes these members by slashing the pupils where the Number signifying their rank is located, creating an "X" shaped scar on the digit, which signifies that they where no longer part of the Twelve Demon Moons. 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 Kyogi losing his apatite for humans and beginning to lose the ability to evolve and become stronger. Therefore, he was deemed to weak to remain in his position of Lower Moon Six.

The Twelve Demon Moons have been given three tasks to complete by Muzan's command:
 * 1) 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 in Chapter 126) that Nezuko is sun-proof, he has decided that the Upper Moons first focus is to capture her and bring her to him.
 * 2) The destruction of the Demon Slaying Corps.
 * 3) After over a thousand years of failing at these two tasks, Muzan has that decided that demons should serve him with suicidal devotion to ensure success.

The Pillars of the Demon Slaying Corps have killed numerous Lower Moons over the years, while the Upper Moons have killed (and eaten) many Pillars as proof of their strength. Kagaya states that its been a hundred years since an Upper Moon has been killed following the defeat of Gyutaro and Daki. Given this, the Lower Moons have been replaced countless times, while the Upper Moon did not change over the course of 100 years. Kibutsuji Muzan decided to dismantle the Lower Moons completely after their most recent failure with the death of Rui (Lower Moon Five). He summoned the remaining Lower Moons to a meeting. Muzan then proceeded to kill the unnamed Lower Moons Two, Three, Four, and Six after their weaknesses were revealed, sparing only Enmu (Lower Moon One) by giving him a chance to redeem himself by killing a pillar with an injection of his blood. But with Enmu's death by the hands of Tanjirou, the Lower Moons are officially disbanded with all of their members dead.

Overview
The first of the Twelve Demon Moons that was encountered in the series was the former Lower Moon 6, Kyogai, who is slain in battle by Tanjiro Kamado. Tanjiro and his companions would shortly thereafter embark to the Natagumo Mountains to face-off against Lower Moon 5, Rui, who was manipulating a group of demons to forcibly act as his family and to assist him in the killing of Demon Hunters. Tanjiro almost managed to behead Rui, but the demon outwitted him by using his threads to cut off his own head. He is later saved by the timely arrival of the Water Pillar, Giyuu 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 Moons by coldly annihilating all members except for Lower Moon 1, Enmu.

Enmu is then given an additional injection of Muzan's blood and then tasked with killing the Pillars and Tanjiro as a last chance offer to save his life, with the promising of even more blood if he were to complete his mission. Enmu later intercepted Tanjiro with his companions on a train. He planned to feast on the 200+ passengers by combining his body with the train and using his Demon Blood Technique to trap them in their own 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 Moon 3, Akaza. Akaza would commence battle with the Flame Pillar, Kyojuro Rengoku. After a lengthy battle, Akaza would emerge victorious, claiming the life of Kyojuro.

Daki, Upper Moon 6, is the next high ranked demon encountered. After receiving word of a demon claiming its feeding ground in the Red Light District, Tengen Uzui (Sound Pillar) sets off with the aid of Tanjiro, Nezuko, Inosuke, and Zenitsu. The group manages to locate Daki and slice her neck off, only for her to reveal her older brother and the true 6th Upper Moon, 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 Moon Six), Muzan summoned the remaining members of the Upper Moons and gave Hantengu and Gyokko (Upper Moons Four & Five, respectively) a mission to exterminate the Swordsmith's Village, to reduce the power of the Demon Slaying Corps by removing their ability to fight on par with the demons without swords. Both Hantengu and Gyokko were slain, but not before Hantengu witnessed (before dying) Nezuko standing in the sun and getting word to Muzan of he fact. This shifted Muzan's maing interest to devouring Nezuko to attain perfection.

After his attack on the Ubayashiki Manor, Muzan escaped into the Infinity Fortress thanks to Nakime. It's revealed that Nakime has replaced Hantengu as the new Upper Moon Four and that Kaigaku (a former demon slayer and fellow apprentice and brother through adoption to Zenitsu Agatsuma) became the new Upper Moon Six after an encounter with Kokushibo, thereby replacing Gyutaro and Daki. It is still currently unknown who the new Upper Moon Five is.

Shortly after arriving in the Infinity Fortress, Shinobu Kocho would stumble upon Upper Moon 2, 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 Pillar and Upper Moon. 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 Pillar, 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 brother, resulting in Kaigaku's death and Zenitsu almost dying. Elsewhere in the fortress Tanjiro and 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 was he finally sedated and passed on.

Doma continues his fight against Kanao, who is unexpectedly assisted by Inosuke Hashibira. He initially overwhelms the two with his ice attributed Demon Blood Techniques, 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 detach Doma's head, putting an end to him.

Love Pillar, Mitsuri Kanroji and Snake Pillar, Obanai Iguro confront the newly appointed Upper Moon 4, Nakime. The demoness outwitted the pairs' attempts by the usage of her Blood Art that warps and controls the entire infrastructure of the Infinity Fortress Dimension as she sees fit. Simultaneously, the Mist Pillar, Muichiro Tokito was separated from the Rock Pillar, Gyomei Himejima by Nakime's ability, falling to the location of the highest-ranking demon, Upper Moon 1, Kokushibo.

Kokushibo instinctively sensed Muichiro because of his blood relation. Muichiro learns of his ancestral relation to Kokushibo, as well as of the demon's former occupation as a Demon Slayer after an examination of his inner body. Kokushibo, impressed by Muichiro's proficiency with his Breath Style, would then unsheathe his sword revealing his Breath of The Moon forms. The attack would sever Muichiro's left arm and he is swiftly defeated with minimal effort. Instead of killing the boy, Kokushibo offers to transform Muichiro into a demon as well due to intrigue in his blood relation and fighting ability. Genya Shinazugawa would attempt to ambush Kokushibo from behind using his shotgun in an attempt to save Muichiro, but his speed proved too formidable for the young Mist Pillar. Genya is immediately dismantled; both arms are sliced off and he is bifurcated at his waist. Given that Kokushibo had encountered a Demon Hunter with very similar physiology about 300 years ago, he knew the way to kill him was the same way a demon is killed, decapitation. However, before Kokushibo could administer the final blow, Genya is saved by the timely arrival of his older brother and the Wind Pillar, Sanemi Shinazugawa.

Sanemi manages to put up a fight against Kokushibo, albeit only for a short moment. After receiving a brutal injury from an attack, Sanemi reveals that he has "rare blood". He intended to use the intoxication of his premium blood as a distraction while fighting but to no avail. Using everything he could manage to think of and was at his wit's end; Sanemi is then almost killed by a barrage of blade swings. The pillar is saved by the intervention of his comrade, Gyomei Himejima (Stone Pillar), the strongest Hunter in the Demon Slaying Corps.