For most stories, demons are considered inherently scary. The ones that show up in Demon Slayer: Kimetsu No Yaiba are quite scary, indeed, with their creepy and unpredictable Blood Demon Arts, and twisted world views. The most powerful of these are handpicked by the demon kingpin Muzan Kibutsuji to gain even more strength by consuming more of his blood, and as many humans as they can get their hands on. Here is a list of the 10 strongest of Muzan’s Demon Moons.
10 Lower Moon Five: Rui
Rui was the first appearance of a real Kizuki, a member of Muzan’s Twelve Demon Moons in DSKNY. Using his Blood Demon Arts, Rui trapped other low-level demons in his web on Mt. Natagumo, transforming and holding them prisoner as a family of spider-demons.
Ranking at Lower Moon Five, Rui caused a good bit of trouble for Tanjiro and Nezuko, pushing them to their limit and drawing out their latent abilities. Even with the help of their ancestors, Tanjiro and Nezuko were only able to hang on by a blood-red thread until the Water Pillar Giyu Tomioka shows up.
9 Lower Moon One: Enmu
Rui’s defeat sparked Muzan to voice his concerns about the Lower Six demons being too weak. Through his display of complete submission, the Lower Moon One demon Enmu survived Muzan’s downsizing of the Lower Six Demon Moons and was given another chance for being a dependable minion worthy of another dose of Muzan’s blood.
Enmu’s Demon Blood Art enabled him to put people to sleep and enter their dreams, lulling his victims to their deaths. He employs this technique by hijacking a train, putting all of its passengers to sleep, and having his own misguided minions enter their dreams to destroy the victims mentally.
8 Upper Moon Six: Kaigaku
As effective as the Demon Slayer Corp is at defending humanity against the demons, not everyone in the Corp has the best intentions. Kaigaku was a former classmate of Zenitsu’s under the Thunder Breath teacher Jigoro Kuwajima. Jigoro hoped for both of his students to become the next Thunder Pillars … and Kaigaku didn’t like that very much.
Able to perform all of the Thunder Breathing Techniques except the first style, Kaigaku wasn’t given the Hashira title and accepted demonification to increase his power. Although inexperienced with Blood Demon Arts, Kaigaku was strong enough to be seated at Upper Moon Six.
7 Upper Moon Six: Gyutaro & Daki
With one of the more tragic backstories, Gyutaro and his younger sister Daki live as one, and so they both were given the Upper Moon Six title. The demon siblings spoke to the strength of the Upper Moons, as it took the combined efforts of Tanjiro, Nezuko, the Sound Pillar Tengen Uzui and his wives, Inosuke, and Zenitsu to put a stop to their antics in the Red Light District.
According to Muzan, Gyutaro was strong enough to win against Tengen and the others but was held back by Daki. With his poisonous Blood Demon Arts, Gyutaro should have had no trouble defeating the Demon Slayers, but Daki represented a human connection — a weakness in Muzan’s eyes.
6 Upper Moon Five: Gyokko
Thanks to his rather fishy obsession with arts and crafts, and his summon abilities, Gyokko was at the very least useful enough to Muzan to assign him the Upper Five rank in the Twelve Demon Moons.
Though flashy, Gyokko’s abilities seemed to be more for esthetic than combat. 14-year-old Wind Pillar Muichiro Tokito was able to dispatch Gyokko quickly and decisively, but only after recovering his memory and activating the Flame Mark.
5 Upper Moon Four: Hantengu
It might be difficult to understand how or why Hantengu is counted among the Upper Moons at first glance, but the DSKNY universe bends the realms of possibility with every demon boss fight. At Upper Moon Four, Hantengu was a struggle for the Love Pillar Mitsuri Kanroji, gun-wielding Genya Shinazugawa, Nezuko, and Tanjiro.
Hantengu’s cowardice functions as a key to his full power. Through Blood Demon Arts, he divides himself into “Primal Emotions,” and when his weakest, fearful self is attacked, his most powerful personality, Zohakuten (hatred), absorbs the other counterparts and attacks his opponents.
4 Upper Moon Four: Nakime
For the first season of the DSKNY anime, not much is seen or heard of the Upper Moon Four demon Nakime, who received a promotion after the defeat of Hantengu. With only a strum of her biwa she can rearrange the Dimensional Infinity Fortress where she resides, instantly transporting herself and others wherever she pleases, so getting a positive I.D on Nakime is very near to impossible.
Nakime’s Blood Demon Art techniques aren’t too dangerous on their own, but her opponents could end up just about anywhere, including a tatami full of hungry demons.
3 Upper Moon Two: Doma
Probably the most sadistic among the Upper Moons is Doma: a grown-up child prodigy. Nothing seemed to be too outrageous for Doma — not his jaw getting blasted to oblivion by Akaza, or even having his body fall apart from a heavy dose of Wisteria poison — he somehow enjoyed every moment of his demonic life.
The Upper Two demon is responsible for the deaths of a few people dear to the Demon Slayers, including Shinobu’s older sister and former Flower Pillar Kanae Kocho, and Inosuke’s mother.
2 Upper Moon Three: Akaza
As the Upper Moon Three demon, martial arts master, and the one responsible for stomping out Flame Pillar Kyojuro Rengoku (and at least one other Pillar), Akaza is one of the most daunting demons to meet in battle.
Akaza has one of the most heart-wrenching backstories as well. He was already a hardened criminal by the time he was a teenager, and for this reason, his sickly father committed suicide. He was also taken in by Keizo, his sensei, and given a chance at turning over a new leaf, but even this promising new life was cruelly stolen from him. This led to Akaza, then named Hakuji, to be labeled a demon even before Muzan found him.
1 Upper Moon One: Kokushibo
A former Demon Slayer from Japan’s Sengoku era, Kokushibo became a demon already having been among the strongest swordsmen in the land alongside his twin brother. His Breathing Techniques combined with Blood Demon Arts earned him the Upper Moon One position.
Kokushibo admits that he became a demon specifically to outlive the expiration date that would likely have come with activating the Flame Mark. He also reveals his relation to Muichiro Tokito; Kokushibo, whose human name was Michikatsu Tsugikuni, had a child before becoming a demon, and he figures Muichiro to be a descendant of that child.