Uppermoons

Muzan Kibutsuji is the main villain of the Demon Slayer: Kimetsu no Yaiba series, known as the first demon, the creator of all others, and the supreme leader of the Twelve Demon Moons.
Origin and History;
Sick human: Over a thousand years ago, in the Heian period, he was a weak young man with a terminal illness that condemned him to die before the age of 20.
Transformation: He killed his doctor in a fit of rage, believing that the experimental medicine didn't work, but then discovered that it granted him strength and longevity in exchange for becoming carnivorous and hating sunlight.
Quest for the Sun: Their great goal for centuries has been to find the blue flower of hell (Blue Spider Lily) to complete the medicine and conquer sunlight. Powers and Abilities.
Extreme regeneration: Can heal any wound in seconds and modify its anatomy with multiple brains and hearts to avoid dying when decapitated.
Shapeshifting: Changes their appearance, gender, or age at will and easily hides among humans with false identities.
Demonic Blood: He can grant power to other humans with a small dose of his blood, although if they receive more than they can handle, their bodies explode.

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Hantengu (Upper Moon Four Original) is the main antagonist (along with Gyokko) of the Blacksmith Village arc. Personality: He is a pathological coward with extreme delusions of persecution. He constantly cries, trembles, and believes he is an innocent victim, despite having been a ruthless thief and murderer in his human life. Power (Emotion Manifestation): His Blood Technique is one of the most complex. When he is decapitated or attacked, his body does not die; instead, it splits into several young and powerful clones that represent his emotions: Sekido (Anger), Karaku (Joy), Aizetsu (Sadness), Urogi (Intense Joy/Pleasure), and the fearsome Zohakuten (Hate), who merges all of the previous ones. The real Hantengu shrinks to the size of a mouse and hides to avoid being decapitated.

Nakime (New Upper Moon Four) Originally the biwa demon who controlled the structure of the Infinite Fortress with the strings of her instrument. After Hantengu's death, Muzan promoted her to Upper Moon Four. Power: She is not a melee fighter, but a tactical strategist. She can alter space, move rooms, teleport people at will, and create floating eyes to spy on demon slayers around the world. Death: During the final battle, Yushiro took mental control of Nakime to use the fortress against Muzan. Seeing that he had lost control over her, Muzan killed her by crushing her head from a distance to prevent her from aiding the demon slayers.

Kaigaku (New Upper Moon Six) is the replacement for Daki and Gyutaro after their deaths. He has a past deeply connected to two important characters. Past: He was an orphan raised in the same temple as Gyomei Himejima (whom he betrayed by letting a demon in). Later, he became a demon slayer, training alongside Zenitsu Agatsuma under the tutelage of the former Thunder Pillar, Jigoro Kuwajima. Upon encountering Kokushibo and being overwhelmed, Kaigaku surrendered and accepted Muzan's blood. Power: He combines Lightning Breathing (from the second to the sixth form) with demonic arts that imbue his sword with black, flesh-cracking electricity. Death: He is defeated single-handedly by Zenitsu in the Infinity Castle, who uses a completely new form of his own creation: the Seventh Form: Burning Thunder God.

Gyokko occupies the position of Upper Moon Five in the Twelve Demon Moons of Kimetsu no Yaiba (Demon Slayer) [Demon Slayer Wiki]. He is the secondary antagonist of the Blacksmith Village arc, characterized by his obsession with art, his grotesque sadism, and his inhuman appearance.
Grotesque Personality and Appearance: Inhuman Aesthetics: His body is the least human of all the moons. He has no normal arms (only small, childlike hands sprouting from his torso and head), his eyes are located where his mouth and forehead should be, and his mouths are where his eyes should be. Artistic Arrogance: He considers himself a supreme artist. He uses the bodies of the blacksmiths he murders to create grotesque "sculptures" and flies into a savage rage if anyone criticizes or ignores his work. Lack of Concentration: His ego is his greatest weakness. During the invasion of the village, he became so obsessed with breaking the concentration of the blacksmith Hotaru Haganezuka (who kept polishing a sword, ignoring the attacks) that he completely neglected his own combat.
Powers and Abilities: Unlike other demons, Gyokko lives and travels through porcelain jars that he can materialize anywhere [Demon Slayer Wiki]. Jar Teleportation: He can instantly travel from one jar to another, making him extremely elusive and difficult to catch [Demon Slayer Wiki]. Marine Summoning: His Blood Technique allows him to summon monstrous creatures with features of fish and octopuses that launch poisonous needles or devour their victims.

Daki and Gyutaro share the position of Upper Moon Six, being the main antagonists of the Entertainment District (Yoshiwara) arc [Demon Slayer Wiki]. Although Daki publicly operates as the public face, Gyutaro is the true power holder and the combat pillar of the two.
Codependency: Gyutaro acts as the tactical and protective mind, while Daki is spoiled, capricious, and emotionally dependent on her older brother's strength.
Powers and Abilities: Daki (Sash Manipulation): Uses his Blood Technique to generate obi cloth sashes as sharp as blades. He can stretch them long distances, use them to fly, store live humans inside them, and control the district from the shadows [Demon Slayer Wiki]. Gyutaro (Blood and Poison Sickles): Fights with a pair of flesh sickles made from his own bones [Demon Slayer Wiki]. His Blood Technique allows him to launch flying blood blades that he can mentally control. Most dangerous is their instantly lethal poison: a single scratch from his sickles is fatal to any human without medical resistance or special techniques.

Kokushibo is Upper Moon One, the oldest, most powerful, and most respected member of the Twelve Demon Moons under Muzan Kibutsuji. Before becoming a demon during the Sengoku period, he was known as Michikatsu Tsugikuni, a demon slayer and the older twin brother of Yoriichi Tsugikuni, the creator of Solar Breathing. Past and Origin (Michikatsu Tsugikuni)
Michikatsu was born into a samurai family. From childhood, he harbored a deep resentment and morbid jealousy toward his younger brother, Yoriichi, who possessed a divine natural talent for swordsmanship that Michikatsu could never match. Despite abandoning his family to become a hunter and develop Moon Breathing, Michikatsu learned that those bearing the Hunter's Mark died upon reaching the age of 25. Desperate to surpass his brother and achieve immortality to perfect his martial arts, he accepted Muzan Kibutsuji's offer and transformed into a demon, abandoning his humanity and his own family.
Powers and Abilities
Kokushibo combines centuries of swordsmanship with unparalleled demonic regenerative abilities. Moon Breathing: He is the only demon capable of using a Breathing Technique. His attacks generate dozens of chaotic crescent-shaped void blades that constantly change size and length, making their trajectory nearly impossible to predict. Kyokyusatsu (Flesh Sword): His katana, called Kyogukamu, is made of his own flesh and bone. He can modify its shape, extending additional blades and branches to attack multiple targets simultaneously. Six-Eyed Vision and Transparent World: He possesses three pairs of eyes that grant him superhuman visual perception. Furthermore, he masters the Transparent World, allowing him to see his opponents' muscles, blood vessels, and movements to anticipate any attack. Despite all this, he can become very intense and active.

Douma is Upper Moon Two within the Twelve Demon Moons of Kimetsu no Yaiba (Demon Slayer) [Demon Slayer Wiki]. He is one of the most sadistic and dangerous demons, characterized by his complete inability to feel human emotions and for being the leader of the "Paradise Faith" cult.
Past and Origin
From his birth in the Edo period, Douma possessed rainbow-colored eyes and platinum blonde hair. His parents, dazzled by his appearance, believed him to be a divine being and founded the Paradise Faith cult, placing him as its leader when he was still a child. Douma never believed in gods and considered those who came to him to unburden their sorrows pathetic. After witnessing his mother's violent suicide (she killed his father for infidelity and then poisoned herself), he felt absolutely nothing, only discomfort at the smell of blood. At the age of 20, he encountered Muzan Kibutsuji, who transformed him into a demon.
Powers and Abilities
Douma is a long-range fighter who uses a pair of razor-sharp war fans made of crystalline gold [Demon Slayer Wiki]. Extreme Cryokinesis: His Blood Technique allows him to generate and manipulate ice and frost at will. Toxic Ice Dust: The air surrounding Douma fills with ice particles so fine that if a demon slayer breathes them in, they destroy their lungs almost instantly, nullifying Breathing Techniques. Ice Clones (Kanisatsu): He can create exact replicas of himself made of ice. These clones are capable of using the same Blood Techniques as the original Douma with the same power. At headquarters, he mostly uses pronouns to annoy Akaza. Using "Akaza-dono" or "Akaza-san," he is uninhibited, mischievous, playful, and feigns most of his emotions.

Akaza is one of the most powerful and tragic Upper Moons in Kimetsu no Yaiba (Demon Slayer). He holds the position of Upper Moon Three, is a master of martial arts, and his greatest motivation is to become stronger. His human history as Hakuji is marked by loss, love, and honor.
Before becoming a demon, Akaza was named Hakuji. He lived in the slums of Edo and stole to buy medicine for his ailing father. After his father's suicide, Hakuji was adopted by a martial arts master named Keizo and fell in love with his daughter, Koyuki. This peaceful life was shattered when a rival dojo poisoned the water well, killing both Keizo and Koyuki. Driven mad by grief and a thirst for revenge, Hakuji massacred the rival dojo before encountering Muzan Kibutsuji, who transformed him into a demon. Personality and Beliefs
Pride in strength: He is a social Darwinist who despises the weak but deeply respects strong warriors, regardless of whether they are human or demon. Respect for names: Once he recognizes a strong opponent, he insists on knowing their name and memorizes it as a tribute to their skill. Akaza's moral code: He is the only demon who refuses to eat or harm women. This stems from a subconscious memory of his fiancée, Koyuki.
"Powers and Abilities"
Fighting Style (Soryu): Unlike other demons, Akaza does not use bladed weapons, but is a master of hand-to-hand combat and martial arts.
Blood Technique (Compass Needle): Creates a snowflake-like pattern around his feet. It allows him to sense his opponent's fighting spirit to predict their movements and instantly find their weaknesses. Martial Arts Techniques: He names his attacks after fireworks, a detail that alludes to the festival he was going to celebrate with Koyuki.