Kokushibo

Kokushibo is a major supporting antagonist of Demon Slayer: Kimetsu no Yaiba. He is a demon affiliated with the Twelve Kizuki, holding the highest position, Upper Rank One (の).

Nearly five centuries ago during the Sengoku Era (the Golden Age of Demon Slayers), Kokushibo was a human by the name of Michikatsu Tsugikuni, a former Demon Slayer and the older twin brother of Yoriichi Tsugikuni, the strongest Demon Slayer that ever existed.

Kokushibo is also the ancestor of Muichiro Tokito and Yuichiro Tokito and the one responsible for turning Zenitsu Agatsuma's senior, Kaigaku, into a demon and joining the Twelve Kizuki.

Appearance
As a demon, Kokushibo took the form of a pale-skinned, tall and muscular man with long and spiky black hair with red tips that he kept in a ponytail. His most notable feature is the three sets of eyes on his face with yellow irises and red sclera that have black straight lines diverging from each iris. His middle set of eyes featurs the kanji of "Upper Rank" and "One". Kokushibo also has red markings resembling flames on the top left side of his forehead and the bottom right of his chin. His appearance was described to be extremely dignified and majestic by the Mist Hashira, Muichiro Tokito.

Kokushibo wore a purple-and-black bee-hive patterned nagagi kimono and black umanori-styled hakama pants tied with a white uwa-obi. He carried a fleshy katana at his waist that had eyes in the space between the tsuka ito wrapping of the handle of his sword. The tsuba and blade were also later revealed to have eyes and veins.

As a human, Kokushibo's appearance was nearly identical to his demon form, with the exception of the number of eyes, his prominent eyebrows, and notably less pale skin. His eyes had brown irises and normal, white sclera as a human. As a child, he was usually seen wearing a white kimono as opposed to the purple-and-black patterned one he is seen wearing as an adult.

After being beheaded by Sanemi Shinazugawa and Gyomei Himejima, Kokushibo evolved into a more grotesque and monstrous form, with protruding fangs, large white horns on the front and and back of his head, pointed nails, red outgrowths on his face, his pupils looking at different directions, shorter and messier hair, several thin tubes poking out of his body, and numerous black and red scorpion tail-like appendages haphazardly growing all across his entire body.

Personality
Kokushibo was often very reserved as a demon, and with such little knowledge about the Upper Ranks, not much was originally known about him. He was an adamant rule-follower, punctual, and he showed a great deal of respect to the hierarchy of the Twelve Kizuki - as seen at the Upper Rank gathering. Kokushibo was portrayed to be humble as well, and he did not hesitate to admit his failure or complain of any difficulty. He displayed a strong sense of loyalty towards Muzan Kibutsuji, with most of his actions being done with the sole purpose of fulfilling Muzan's goals. Despite exhibiting outward reservation and humility, he was also rather cold; his words could be extremely harsh, especially when reprimanding individuals. His threats came off as nothing short of cruel and overwhelmingly serious, and he demanded absolute obedience.

Kokushibo has also been shown to be genuinely delighted when the opponents he faced challenged him; such as helping dress Muichiro Tokito's amputated hand over his talented swordsmanship, praising Gyomei Himejima for his unparalleled human abilities and sparing Akaza because he enjoyed the challenge of battling him. However, due to this, he also felt irritation after he realized he died and he pitied Gyomei for his impending death from unlocking his Demon Slayer Marks.

He had a complex relationship with his human past. He showed something of warmth towards his descendant, Muichiro, commending his skills and resolve, and moved to convert Muichiro into a demon to spare his life. At the same time, he referred to Muichiro and his abilities as the natural result of his "cells" being passed down.

In his duel against Gyomei, the demon's banter suggested a fear of death. When Gyomei's marks appeared, Kokushibo preemptively bemoaned the loss of a talented fighter and urged him to become a demon to continue honing his skills. He seemed surprised when Gyomei vehemently rejected his offer and called his mentality pathetic.

It was revealed that as a human, Kokushibo harbored an immense sense of envy towards his younger twin brother, Yoriichi Tsugikuni, for his natural talent and incredible abilities. These feelings of jealousy and contempt strengthened upon seeing his brother aged to an old man despite Yoriichi awakening his Demon Slayer Mark, which was to supposedly doom him to die at the age of 25. However, despite this immense jealousy, spite, and outright hatred he harbored for Yoriichi, he still deeply cared for and loved his brother, as seen when he was touched by Yoriichi treasuring the handmade flute he had made for him as children. Kokushibo shed genuine tears over his brother's death, and even went as far as keeping the flute itself for the following centuries as a memento to his beloved and hated younger brother.

Likely a result of his inferiority complex and his immense desire for strength, Kokushibo feared the prospect of suffering defeat. So much so, he became increasingly more aggressive and agitated when being pushed further into a corner, causing him to become more desperate in his attacks and the use of his demon power. During his battle with the Hashira, he came to realize the steep price he had paid for the strength he so much desired, becoming an ugly monster far from from his idealized dream of becoming the strongest samurai just like his brother, symbolizing how much his deep ambitions and resentment had warped him for the worst. Moreover, his overinflated desire to surpass his brother is even shown in the form of his six eyes, which imply his desperation to attain the Transparent World in order to exceed his brother. Later upon his death, he greatly lamented and regretted his choices in his life and began to openly question himself if the path he walked was truly the right one. Kokushibo died without knowing why he was ever born, and was full of regret and sorrow for not being able to accomplish anything that he had wanted.

Abilities
Overall Abilities: Kokushibo was an extraordinarily powerful demon, proven to be the strongest of the Twelve Kizuki and the second strongest demon in existence, just behind the Demon King, Muzan Kibutsuji himself. As one of the oldest demons in the series, he had battled numerous Demon Slayers and obtained vast experience and knowledge of combat. He was able to easily decipher the techniques and skills of at least two Hashira and overwhelm them in battle. His physique is one of the most polished and immense in the existence, as not only is he a user of Total Concentration Breathing, but also a marked individual as well as a member of the Twelve Kizuki who possesses the highest concentration of Muzan's physique enhancing blood in the organization.

These overall abilities and skills allowed Kokushibo to defeat two Hashira with minimal effort and then fight against both Sanemi and Gyomei, the latter of which was considered to be the most powerful Demon Slayer in the Demon Slayer Corps in the current generation. Even when Gyomei and Sanemi awakened their Demon Slayer Marks, which increased one's physical abilities way above their normal limit, he was still capable of holding his own against the both of them simultaneously.

As a testament to his might, it ultimately took a combo of attacks from Gyomei Himejima, Sanemi Shinazugawa, Muichiro Tokito and Genya Shinazugawa, all whom were exceptionally strong individuals, to even land a significant injury on him. He was so strong that the only way that the Demon Slayers had a chance at winning was to immobilize him, which took the lives of Muichiro and Genya, the latter needing to use a Blood Demon Art in order to do so, meaning that normal attacks wouldn't work against Kokushibo at all. Toward the end of their fight, he even acquired the ability to regenerate his severed head, leaving the sun as his only weakness. Ultimately, Kobushibo's loss was mostly a result of his resolve wavering upon realizing that his lust for power had turned him into a monster, causing him to stop regenerating, rather than the skills of his opponents.

Biological Absorption: Kokushibo possesses the ability to absorb human and demon bodies through physical contact. Although this trait has never been displayed, its stated that Kokushibo would absorb the demons that challenged him and were defeated. It can likely be assumed that he uses this method as a faster alternative of consuming humans, or Demon Slayers.

Demon Slayer Mark: Kokushibo awakened his mark when he trained under Yoriichi. Its specific abilities are unknown, but what is know is that it drastically improves the abilities of the Demon Slayer, making them much stronger and faster than what they can achieve normally, though at the cost of being cursed to die at the age of 25. As a demon, Kokushibo is no longer bound by the curse, as demons are immortal.
 * Transparent World: Similar to Yoriichi, Kokushibo has not only gotten access to the Transparent World, but also obtained the ability to constantly use it. This allows him to see the muscles, blood flow, and joint movement of his opponents. He can accurately predict and anticipate the movements and attacks of his opponents with this ability. He was also able to identify that Muichiro was his descendant, immediately discern the skill level of Muichiro, Sanemi, and Gyomei with one look, and see that Genya consumed demons to gain strength.

Extrasensory Perception: Kokushibo can detect presences of others outside of his range of perception, as shown when he dodged Genya's gunshots and appeared directly behind him despite Kokushibo not looking at Genya at all. With the Transparent World, he could perceive the bodily structures and see through the bodies' of his opponents and use this information to predict their attacks and movements. He also seems be extremely proficient in the use of the Transparent World, being able to trace back the heritage of a young child back to his own bloodline with a simple glance. He's also able to immediately determine how strong his opponents are by looking at their muscles and bodily structure. Outside of his vision, Kokushibo also seems to be able to keep track of the locations of his peers around the Infinity Castle, evident as he no longer felt Akaza's presence when he died.

Flesh Manipulation: Like all demons, Kokushibo possesses the ability to manipulate his own flesh, although at a much higher caliber since he assimilated a lot of Muzan's blood. He used this ability to grant himself multiple eyes that augment his vision to superhuman levels. He has also used this ability to create an extremely durable and sharp katana, complete with a handguard and scabbard. Because of this, his katana can never be destroyed as he can regenerate it like he would with normal wounds.
 * Sword Manipulation: As an extension of his flesh manipulation ability, Kokushibo can manipulate a detached part of his body in the form of his katana. This allows him to easily regenerate parts of if it was destroyed or damaged as he would his body, which was shown numerous times when the blade returns to its original shape when Gyomei or Sanemi damaged it with their attacks. Furthermore, he can freely manipulate the form of the blade, shown when he grew three additional blades from the original blade to increase its reach and further increase its size, turning it into a weapon similar to the Shichishito (Seven-Branched Sword). Later, Kokushibo also displayed the ability to grow and protrude multiple blades from his own body, allowing him to perform a multitude of slashes from them without a swinging motion. This attack was powerful enough to easily blow away two Hashira and destroy Genya's Blood Demon Art, as well as slice in half numerous columns in the room, from just its activation.

Immense Durability: Kokushibo had displayed immense physical durability as seen when despite Gyomei using both his flail and axe to attack both ends of his neck, it still didn't budge. His neck was only severed thanks to both the combined efforts of both Gyomei and Sanemi putting all of their strength into forcing his neck to be sliced with Gyomei's axe, along with both of their weapons turning bright red, which further hampered his regeneration.

Immense Regeneration: Kokushibo possesses one of the most powerful regenerative abilities in existence, second only to the Demon King, Muzan Kibutsuji. His regeneration speed is even faster than Akaza and Doma, regrowing his ear and right arm nonchalantly and effortlessly. Later, upon being decapitated by two marked Hashira, Kokushibo was able to regenerate his entire head and successfully conquered death by beheading after being decapitated by Nichirin Swords, a feat considered impossible for demons and only accomplished by two other demons: Akaza and the Demon King himself. However, while the speed at which he regrew his head was far faster than the former, his regeneration after being decapitated became unstable, causing him to take on a monstrous visage.

Immense Speed & Reflexes: Kokushibo possessed immense levels of speed most likely far surpassing that of all his other Upper Rank brethren, as shown when he slashed off Akaza's arm before he, or any of the other Upper Rank demons present, realised. He displayed his phenomenal speeds on multiple occasions. Firstly, he was able to effortlessly outpace Muichiro's Mist Breathing techniques, moving so fast it seemed like he teleported. Muichiro himself stated that Kokushibo's speed was in another dimension compared to his own, despite being marked. When Genya used his shotgun to shoot the Upper Rank from a distance, Kokushibo managed to "teleport" right to his location before the bullets could reach him, even having his arm sliced off the moment he arrived. Afterwards, he slashed off his other arm and his torso so fast that it made it seem like he didn't even move.

Later when his bout with Sanemi began, he could easily keep up with his techniques and movements despite the latter having to exert himself to the limit in order to stay alive. When Sanemi used his brother's shotgun to shoot at the Upper Rank, Kokushibo was fast enough to block the bullets even when the shotgun was very close to him. After feeling the need to try harder, Kokushibo subdued the Wind Hashira with a single technique that was fast enough that he couldn't evade in time, delivering a multitude of cuts and slashes all across his body. Against Gyomei, the strongest Hashira of the current generation, Kokushibo was still more than capable of keeping up with his unorthodox attacks. Even after both Hashira were marked, an enraged Kokushibo could unleash sword attacks that even they couldn't fully react to. His speed posed such a threat towards his opponents that Muichiro had to sacrifice a leg in order to stop the Upper Rank from moving so that Genya can fully immobilize him with his Blood Demon Art.

Immense Strength: Kokushibo has displayed immense physical strength, lifting a gigantic sword much heavier than a regular katana and swinging it incessantly at speeds faster than the eye can see without rest or much effort. Kokushibo also managed to slice off Muichiro's arm with his bare hands. Since he assimilated more of Muzan Kibutsuji's blood than Upper Rank Three, Akaza, a demon that can shatter the ground and kill people with his bare fists, it can be assumed that Kokushibo possessed greater, or comparable, physical strength to him.

Indomitable Will: Solely because of his goal to surpass his younger twin brother, Yoriichi Tsugikuni, Kokushibo possesses a superhuman willpower an indomitable spirit. When he was about to get killed, he forced his regeneration to evolve, and regrew his own head along with a myriad of enhancements, all because he didn't allow himself to die until he accomplished his goal.

Menacing Aura: Kokushibo possesses a menacing and overwhelming presence that made Muichiro, a Hashira who has defeated countless demons in the past, lose the will to fight and caused his body to tremble uncontrollably.

Monstrous Transformation: Later, upon re-growing his head while battling Gyomei and Sanemi, Kokushibo was able to transform himself into a more monstrous form with several appendages on his back that enhanced all of his abilities and powers to nearly the same level as the Demon King, Muzan Kibutsuji. Kokushibo stated that any attacks thrown at him in this state would be meaningless, and that the sun would be the only way to kill him.

Tactical Intellect: As a talented swordsman who has existed for over four centuries, Kokushibo has experienced countless battle situations and threats which he has learnt to overcome and circumvent. This was displayed during his battle with three Hashira and Genya, where he was able to adapt to their special and unique fighting styles and tactics nigh instantaneously after witnessing it. For example, after Muichiro unleashed his first attack against the Upper Rank, he was able to determine he was a user of Mist Breathing, a talented one at that. This was further accentuated through Kokushibo being able to take on Sanemi and Gyomei simultaneously despite both of them being marked and being users of different Breathing Styles, meaning he’d have to deal with 2 vastly different opponents at once, which he did so successfully, even overwhelming them multiple times.

Unlimited Stamina & Endurance: Kokushibo possesses absolute and infinite stamina and vitality, never tiring and always remaining in optimal physical and mental condition all the time as well as being able to endure waves of onslaught as if it were nothing. Despite having his ear, then limbs and whole chunks of his body being repeatedly torn off and destroyed, he never once showed a sign of pain or agony. Even when his head was being crushed by Gyomei Himejima's spiked flail, he remained resilient.

Blood Demon Art
Crescent Moon Blades: Complementing his combat style: Moon Breathing, his Blood Demon Art allows him to create and manipulate dozens of sharp blades shaped like traditional crescent moons from his flesh katana. They are implied to be created from his blood and can be either a bright yellow or a bright blue in color. These crescent moon blades are extremely chaotic, constantly changing in size, length and speed, making Kokushibo's attacks extremely unpredictable and unreadable as they have no set pattern. This Blood Demon Art greatly enhances the power of his techniques, making every single one of his sword swings extremely deadly and dangerous. He also seems to be capable of using his Blood Demon Art as long as his katana is unsheathed, allowing him to create crescent moon blades even without swinging his sword or unleashing a technique. The volatile nature of his Blood Demon Art makes it extremely challenging for Demon Slayers to circumvent. Sanemi stated that if not for his years of experience in the field of demon hunting, he wouldn't have been able to defend himself from Kokushibo's attacks.

Kokushibo's Blood Demon Art seems to have a secondary ability which allows him to manipulate the shape and range of his sword slashes when unleashing his Moon Breathing techniques. His slashes usually create and are surrounded by a red/orange crescent shape that carry his crescent moon blades. Kokushibo seems to be able to control said slashes to a certain extent, increasing their range and shape to attack his target in impossible ways under normal circumstances. When he distorted his katana into its branch-like appearance, his slashes turn into a light purple color. Kokushibo displayed the ability to exponentially increase the range of his sword slash with his Moon-Dragon Ringtail technique and shape his slashes into a circular drill-like shape with his Drilling Slashes, Moon Through Bamboo Leaves technique.

Fighting Style
Master Swordsman: Due to training and refining his swordsmanship skill for over 400 years and getting a major boost to his physical capabilities, Kokushibo has become the most powerful and skilled swordsman in the modern era, and the second strongest swordsman in existence, behind his younger twin brother, Yoriichi Tsugikuni. As a Demon Slayer in the golden era, his swordsmanship was already outstanding as he learnt them from Yoriichi himself and later stated that their techniques were so refined and legendary that they have no hopes of it being passed down for future generations.

Kokushibo's skill in the blade allowed him to defeat Akaza, a prodigy at hand-to-hand combat and martial arts, as well as Doma. With his exceptional sword wielding skill, he could singlehandedly take on Sanemi, Muichiro and Gyomei when they were marked as well as Genya when he assimilated his blood and gain a small portion of his power and had access to Blood Demon Arts. Kokushibo's swordsmanship was further empowered with the development of his own Blood Demon Art, which greatly improved the lethality and power of his techniques, making every single one of his sword swings incredibly deadly.

Swordsmanship
Moon Breathing (の): Kokushibo was the first demon that utilized Breathing Styles. His Breathing Style, in particular, is one of the most dangerous and powerful ones displayed thus far. Enhanced with his Blood Demon Art, he can create many chaotic crescent moon blades when slashing that vary in length and size in crescent shaped sword attacks. Kokushibo had continued to develop this Breathing Style and had created over a dozen techniques over the centuries he had lived.


 * First Form: Dark Moon, Evening Palace (ノ　・の) - Kokushibo quickly draws his sword and slashes swiftly in a singular horizontal motion in a crescent shape, creating numerous chaotic crescent blades. This technique is extremely reminiscent of Iaijutsu.


 * Second Form: Pearl Flower Moongazing (ノ　の) - Kokushibo performs several crescent-shaped slashes that defend him from incoming attacks, sending a barrage of crescent blades.


 * Third Form: Loathsome Moon, Chains (ノ　・り) - Kokushibo swings his sword rapidly in two gigantic crescent slashes, from which a storm of smaller crescents spread, causing huge destruction in a small area.


 * Fifth Form: Moon Spirit Calamitous Eddy (ノ) - Kokushibo makes multiple curved slashes layered over one another, creating a rising vortex of sword slashes and crescent moon blades.


 * Sixth Form: Perpetual Night, Lonely Moon - Incessant (ノ　・) - Kokushibo releases a wild barrage of crescent-shaped slashes several meters in front of him. This technique was powerful enough to overwhelm Sanemi Shinazugawa and so long-ranged that it slices up the surrounding pillars.


 * Seventh Form: Mirror of Misfortune, Moonlit (ノ　・え) - Kokushibo swings the gigantic version of his sword in a powerful frontal crescent-shaped slash that creates powerful multi-directional long-ranged slashes in the ground.


 * Eighth Form: Moon-Dragon Ringtail (ノ) - Kokushibo uses the gigantic version of his sword and creates a singular gigantic crescent-shaped slash that slowly decreases in size, creating dozens of crescent moon blades.


 * Ninth Form: Waning Moonswaths (ノ　り・) - Kokushibo creates a stream of long-ranged crescent-shaped vertical and horizontal slashes along with numerous crescent moon blades with the gigantic version of his sword.


 * Tenth Form: Drilling Slashes, Moon Through Bamboo Leaves (ノ　・) - Kokushibo creates a long-ranged triple-layered slash twister full of crescent moon blades with the gigantic version of his sword.


 * Fourteenth Form: Catastrophe, Tenman Crescent Moon (ノ　・) - Kokushibo uses the gigantic version of his sword and creates a chaotic vortex of powerful extremely long-ranged omni-directional slashes that destroys whatever is caught up within its attack radius.


 * Sixteenth Form: Moonbow, Half Moon (ノ　・れ) - Kokushibo creates a barrage of downward crescent slashes from an extremely long and wide range, resulting in a powerful six-fold slash crashing down on his opponents; the attack itself is powerful enough to create several miniature craters where the slashes have landed.

Equipment
Flesh Katana: Kokushibo carries a fleshy and demonically modified version of a Nichirin Katana he used when he was a Demon Slayer. As suggested by its appearance, the katana is created from the flesh and blood of Kokushibo himself and due to his body's immense durability and hardness, his katana is as sharp, if not more, than a regular Nichirin Sword. His sword is fleshy red in color, akin to the color of blood, with veins and his eyes all around the blade and even the hilt. However, it is unknown whether those eyes can be used to extend his vision. His katana's hilt is circular shaped with 4 slight indentations, a center with 3 eyes and several black veins and a golden border. He also carries a sword sheath at his waist that has the same fleshy appearance as his katana. According to the second databook, Kokushibo named his flesh katana "Kyokokukamusari".

Trivia

 * Kokushibo's alias contains the On'yomi/reading of the kanji for "black" and the Kun'yomi/reading for "death" and "eye".
 * Kokushibo's human family name contains the Kun'yomi/reading of the kanji for "to inherit, succeed" (継) and "country" (国), while his first name also contains the Kun'yomi/reading of the kanji for "sterness, severity" (巌) and "to prevail, victory" (勝).
 * Kokushibo has been challenged three times for his position. One of these battles involved Akaza. While Kokushibo would usually absorb the demon he defeated, he let Akaza live because he enjoyed the challenge.
 * Kokushibo is presumably the first Demon Slayer to become a demon.
 * He became a demon in his early 20s and lived as such for additional 460+ years.
 * Kokushibo once killed a leader of the Demon Slayer Corps. This caused the corps to put extreme effort in hiding the residence of future leaders. This event was also the one that caused the Kakushi to be formed.
 * Kokushibo ranked 14th in the second popularity poll with 2938 votes.
 * The relationship between Yoriichi and Michikatsu parallels the mythology of the Shintō deities Amaterasu and Tsukuyomi, respectively. Amaterasu is the most sacred of Shintō deities, the sun goddess. Tsukuyomi, the moon god, is her former husband and brother. After Tsukuyomi killed Uke Mochi, another shintō deity, Amaterasu refused to ever look upon him again, moving to another part of the sky and beginning the cycle of day and night. Like the deities, the siblings also feud and have chosen different paths (that of the Demon Slayer and the demon), developing their respective breathings of the sun and moon.

Quotes

 * (In regards to Akaza) "Akaza's presence is gone. He has fallen. Akaza... weren't you going to defeat me? A path had open for him to attain further heights... but he renounced it himself. How exceedingly weak."
 * (To himself) "The old and ugly creature that was once my little brother had pity for me. But... I wasn't angry. Even though 60 years ago, he had been such an eyesore. The voice calling me "brother" was terribly hoarse. My brother had never shown the slightest emotion... so at the sight of him shedding tears, something welled up in me for the first time since birth. I was confused... at my own unexpected unrest. But I must kill... this part of me from when I was human... This old man of brittle flesh past his prime... He was a Demon Slayer, and I must cleave anyone who turns a sword upon me. But his odd sentimentality... disappeared the next moment."
 * (In response to Yoriichi Tsugikuni's statement about future generations) "Yoriichi... when you smiled, I couldn't help it... but I always found it disturbing. And when we were talking about how there were no successors for the various breathing techniques you suddenly started viewing things with strange optimism and you smiled. In my conceit I believed that only our generation was special. I felt sick with disgust and irritation. What did you find so amusing? [...] What is so amusing about imaging such a future? Just thinking about losing makes me boil with anger."
 * (To himself) "The ugliness of not admitting defeat even though they took my head, chopped me up and crushed me. Living in disgrace. Have I lived hundreds of years for this? Was I so afraid of defeat that I became a monster? Did I want to be strong even if it meant eating people? Did I become this miserable creature because I didn't want to die? No. Yoriichi... I just wanted to be you."
 * (To himself) "I could never grab hold of anything. Anything at all. I abandoned my home. I abandoned my wife and children. I abandoned my humanity. I cut down my descendants and abandoned being a samurai. But even all that wasn't enough? You said that those who master their paths all reach the same place. But I never did. I could not see the same world that you did. Why could I not leave anything behind? Why could I not become someone known? Why are we so different? Why in the world was I ever born? Tell me... Yoriichi."

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