The Twelve Kizuki (or 12 Demon Moons) in Demon Slayer are the strongest demons of Muzan, separated into Upper and Lower Ranks (I-VI), each one being empowered by his blood, controlling extreme arrogance, power and sometimes tragic background history (such as the envy of Kokushibo, the emotionlessness of Doma and the poverty of Gyutaro).
Their character analysis gives us themes of unfettered pride, human suffering experienced in the past, and then the eventual coming of the tenacious friendship-driven Slayers to take advantage of their unfettered pride and slow adaptation.
Overview
The Twelve Kizuki is a body of the 12 strongest individuals amongst the demon-kind, with a strength and authority second only to the Demon King himself, Muzan.
Each member of the Twelve Kizuki have received a large part of Muzan’s blood, more so than any other demon therefore exponentially raising their power.
As a testament to this, every member of the Twelve Kizuki can utilize Blood Demon Arts; supernatural powers and techniques manifested through his or her blood that only significantly powerful demons have access to.
The Twelve Kizuki are thus split into two groups, the six Upper Ranks, numbered 1-6 and the six Lower Ranks, also numbered 1-6. The number represents their position amongst the Twelve Kizuki, based on each member’s degree of strength, Upper Rank One being the strongest member and Lower Rank Six being the weakest.
The numbers and ranks of the Lower Ranks is only engraved into one of their eyes, while the numbers and the kanji of ‘Upper Rank’ are engraved into their eyes.
When a member of the group is removed from the Twelve Kizuki Muzan demotes these members by slashing the pupils where the number indicating their rank is located thus creating an “X” shaped scar over the digit signifying it is no longer part of the Twelve Kizuki.
The only example of this happening would be that of Kyogai who had already reached his “limit” and could not consume human flesh anymore. This slowly began to make Kyogai lose his taste for humans, and began to lose the ability to evolve and become stronger.
Therefore, he was not considered strong enough to keep his position as Lower Rank Six and then removed.
Mission
The Twelve Kizuki have been assigned by Muzan’s orders to accomplish three tasks:
1) To find the Blue Spider Lily (the key ingredient used to make up the experimental medicine that made Muzan a demon), but since Muzan’s discovery (through Hantengu) that Nezuko Kamado is immune to the sun, he has decided that the first focus that the Upper Ranks will take is to capture her and bring her to him.
2) The annihilation of the Demon Slayer Corps. As a part of their mission to destroy the corps, Muzan gave the Twelve Kizuki specific orders to hunt down and get rid of the Ubuyashiki Family (as they are the leaders of the corps and support them) and as a whole as they are ultimately what keeps the Corps alive and allows them to rebuild the organization again and again no matter how many times Muzan and the Twelve Kizuki try to destroy it.
3) After failing at these two tasks repeatedly for centuries, Muzan has decided the Twelve Kizuki should serve him with suicidal devotion to see to success at this point.
Blood Battle
According to Kokushibo, if there is any dissatisfaction between the members of the Upper Rank demons, they must invoke the right for the lower ranked demon to kill or defeat their desired targeted in order to elevate their position in the hierarchy.
Any that defies the rules will have to face retribution, when Kokushibo chopped off Akaza’s arm by way of warning against attacking Doma and ignoring 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 show them favoritism and give them special privileges normally not given to average demons.
One of these privileges is that he would empower all members of the group with large 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 right to turn humans they consider worthy into demons by gifting them blood and on receiving the permission of Muzan, their blood will then turn to his blood.
This was seen in the case of Doma when he turned Gyutaro and Daki into demons by giving him his blood and Kokushibo when he turned Kaigaku into a demon by giving him his blood.
As seen from the case with Rui, Muzan gave him special permission to compose a large group of demon, despite his own law of forbidding them to team up together in large numbers, in an attempt to fulfill his longing for a family.
This shows that despite his paranoia of other demons working together in overthrow him, his favoritism for Rui exempted himself from this law and allowed to his “family” to exist.
With Gyutaro and Daki he presented them with the special privilege of sharing the post of Upper Rank Six.
His favoritism to Gyutaro was the main cause for this and he brushed aside the reality that he perceives their emotional attachment to each other as weakness and does not really accept Daki as a Upper Rank.
With Akaza, Muzan gave him such special permission not to eat woman. Akaza was noted by Doma to have odd 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 commands for the Twelve Kizuki to strive for more power continuously by eating humans in mass to be better use to his plans, Muzan actually gave Akaza special permission to not eat women and indulged to his unusual quirk due to considering him to be one of his favorite Upper Ranks.
Akaza was also favored by Muzan to a point that he was only deployed for special assignments and nothing else, a right not given even to the two demons that ranked above him.
