Kyojuro Rengoku

Kyojuro Rengoku was a major supporting character of Demon Slayer: Kimetsu no Yaiba and a major character in the Mugen Train Arc. He was a Demon Slayer of the Demon Slayer Corps and the former Flame Hashira.

Appearance
Kyojuro was a young adult of tall stature and athletic build. He had long bright yellow hair with red streaks with two shoulder-length bangs and two chin-length bangs on the side of his head, black forked eyebrows, and golden eyes that fade to red with white pupils.

Kyojuro wore a paler brown version of the regular Demon Slayer uniform, which consisted of a brown gakuran jacket, a white belt around his waist, and hakama pants. Over this, he wore a haori with a white-yellow gradient pattern and red flame-like ridges at the end that his father Shinjuro once worn and more than likely his father worn when they were the Flame Hashira respectively. Finally, he wore red tabi socks with yellow flames erupting from the bottom up, with a pair of white zōri with red straps.

Personality
Kyojuro was greatly enthusiastic regarding his duties as a Hashira and often came across as cheerfully eccentric. He was amiable, pure of heart, and boasted extraordinary technique and swordsmanship stemming from strict practice and discipline. He was an honorable warrior who adhered to his code of morals and principles that was instilled into him by his mother at a young age—the most significant being his belief that those who were born strong must protect the weak.

Abilities
Overall Abilities: As a former Hashira of the Demon Slayer Corps, Kyojuro was a very powerful swordsman. Even Demons as strong as Akaza, Upper Rank 3 and the fourth-strongest of the known Demons, acknowledged Kyojuro's strength. He even went as far as to offer to turn Kyojuro into a Demon so he could surpass his human limits and become stronger, something he only offered to swordsmen whose abilities he believed were refined to their utmost.

Physical Abilities
Immense Strength: As a former Hashira who spent years perfecting his physical prowess, Kyojuro possessed amazing physical strength, being capable of swinging his katana at speeds faster than the eye can see incessantly and terrifying accuracy while engaging in combat. Kyojuro also possessed a caliber of grip strength that was able to hold down Upper Rank 3, Akaza, one of the strongest characters in the series, despite having his Solar Plexus pierced earlier, to the point that Akaza expressed his disbelief and shock over the strength he describes as "unbelievable".

Immense Speed & Reflexes: Kyojuro possessed great speed and reflexes that even a trained and gifted Demon Slayer like Tanjiro couldn't perceive or register. Kyojuro could even cause tremors to the ground and nearly launching a train off its tracks by running at speeds faster than the eye can see. His reflexes were so fast that he managed to cut Akaza's hand in half moments before the Upper Rank was going to kill Tanjiro. Kyojuro also managed to keep up with Akaza's high-speed techniques, which even the Hashira remarks are faster than the blink of an eye, sometimes even managing to out-speed him. Inosuke Hashibira himself noted that Kyojuro was in a different dimension due to his blinding attacks and speed. Kyojuro's phenomenal movement speed and reflexes even surprised and impressed Akaza, who openly expressed his amazement.

Immense Stamina & Endurance: Kyojuro displayed superhuman stamina and endurance during his battles over the course of the series. In his battle against Enmu when he fused with an entire train, he was able to keep him at bay in 5 different train carts without tiring. Lastly, he managed to keep up with his strongest opponent yet, Akaza, despite physically and mentally exert himself beyond his limit and sustaining multiple irreversible and fatal wounds, like a smashed eye, shattered ribs, and damaged internal organs. Most impressively, he managed to keep Akaza at bay despite having his vital spot, his Solar Plexus, pierced by the Upper Rank's arm and bleeding out. Despite all of his fatal wounds and injuries, he never once flinched or showed signs of pain or agony.

Mental Abilities
Tactical Intellect: As a swordsman who came from a lineage of Flame Hashira, Kyojuro had access to generations of combat knowledge and tactics as well as training from previous Flame Hashira, like his father, Shinjuro Rengoku. During the battle against Akaza, he displayed keen judgment. For example, after being attacked by Akaza's Destructive Death: Air Type, he realizes that he must fight at close range with the wanted to increase the chances of cutting off his head. Even when the usually deductive and sagacious Tanjiro Kamado was at a loss of how to kill Enmu, Kyojuro instinctively knew that no matter what form a Demon takes, it will always have a weak spot. He also possesses great knowledge in the use of Total Concentration Breathing, knowing how to plug minor wounds and hemorrhaging, and saved Tanjiro from dying of blood loss.

Supernatural Abilities
Enhanced Senses: Like all skilled Demon Slayers, Kyojuro had incredibly honed senses, such as when he was able to sense and perceive Akaza's immense presence and demon aura which he uses to discern that he was an Upper Rank. Kyojuro was also capable of sensing demonic presences faster and more accurately than Tanjiro Kamado, who harbors an acute sense of smell when he detected two demons right after another on a train before anyone else noticed. This ability also allowed him to precisely gauge the regenerative abilities and weaknesses of most Demons, like Enmu.

Miscellaneous Abilities
Indomitable Will: Kyojuro had an undaunted spirit, which even impressed the likes of Upper Rank 3, Akaza. Ever since he was a child, he had inculcated indomitable will and passion in himself due to his promise to his late mother. This was best displayed during his fight against Akaza. Even when the Upper Rank overwhelmed him with powerful attacks, giving Kyojuro insidious wounds, he remained steadfast resolute. After Kyojuro lost an eye and had internal wounds caused by Akaza, he persisted, vehemently expressed his unwavering will and determination, saying that he will protect the lives of the other innocent people no matter what. Finally, when Akaza's fist pierced his solar plexus, it triggered a memory in his psyche, reminding Kyojuro of his mother again, giving him the final push to cut the Upper Rank's head, even stopping his fists from moving. But alas, his efforts were in vain, but the incredible determination Kyojuro displayed, affected Tanjiro Kamado greatly, giving him the incentive to push on.

Fighting Style
Master Swordsman: As he was a Hashira of the Demon Slayer Corps, Kyojuro was one of the most powerful and skilled swordsmen in the entire organization. His mastery of the blade is best showcased during his battle with Akaza, in which he can hold his own against the Upper Rank even when gravely injured.

Flame Breathing: Taught to him by the previous Flame Hashira, Shinjuro Rengoku, Kyojuro became extremely proficient in his skill with this particular combat style, being able to go toe-to-toe with Upper Rank 3, Akaza."First Form: Unknowing Fire - The swordsman charges towards their opponent at high speed and decapitates them in one slash so powerful that it generates enough friction and heat it burns the flesh of their enemy. This technique had enough force to launch the entire Infinity Train off the tracks a short distance.""Second Form: Rising Scorching Sun - The swordsman releases an arching slash attack upwards.""Third Form: Blazing Universe - The swordsman swings their blade downwards in an arc.""Fourth Form: Blooming Flame Undulation - The swordsman swings their blade in a circular motion that can defend them from all incoming attacks or decapitate multiple enemies at once.""Fifth Form: Flame Tiger - The swordsman unleashes a powerful series of sword slashes that takes the form of a rampaging tiger engulfed in flames that charge towards the enemy at blinding speeds.""Ninth Form: Rengoku - The most powerful Flame Breathing technique. A devastating dashing slash that the swordsman initiates from a high stance, the technique had enough power to carve a deep impression that burnt the ground where it was unleashed. In the movie adaptation, this attack takes the form of a titanic flaming dragon with blue eyes that emits blue streaks of electricity from its mouth. After this technique is performed by Kyojuro in the movie, the surroundings were seemingly engulfed in flames, creating a purgatory-like hellscape and a giant whirlwind of heat and fire in the wake of the attack."

Equipment

 * Standard Nichirin Katana: Like the majority of Demon Slayers, Kyojuro harbored a standard Nichirin Blade. His katana is a deep shade of reddish-orange in color with the words Destroyer of Demons engraved on the side. His katana's hilt is shaped like a flame with a red core and golden border.

Trivia

 * Kyojuro's surname means "purgatory" ( rengoku?). His first name contains the kanji for "apricot" (杏 kyō?), "longetivity" (寿 ju?)", and "son" (郎 rō?).
 * Kyojuro's rankings in the popularity polls are as follows:
 * Kyojuro ranked 7th place in both the first and second popularity poll with 1,021 votes and 8,000 votes respectively.
 * Kyojuro loved to watch sumo wrestling.
 * Kyojuro's favorite food was sweet potatoes. When eating them, he said "tasty/delicious" (い umai?) each time he puts one in his mouth.
 * His favorite side dish was salt grilled bream.
 * Kyojuro was never allowed to have a pet because his father hated animals.
 * Kyojuro's very distant ancestor, as stated by Kyojuro, ate a lot of tempuras causing their descendants' and their own hair to become quite abnormal.

Quotes

 * (To a Demon) "However, if you bare your fangs at innocent people, my bright red flame blade will burn you to the bone!"
 * (To himself) "Life is a series of decisions. You never have unlimited options... or unlimited time to think, but... what you choose in that instant defines who you are... Warriors who strive to save other people's lives are precious. Their pure and single-minded dedication is separate from their natural talent. They don't risk their lives to earn praise. They simply feel that they must. What they choose in that moment, is a cry from the depths of their souls. Isn't that right... my friends?"
 * (To himself) "I can't believe it! As a Hashira, I'm ashamed of myself! If there's a hole, I want to go into it!"
 * (To Senjuro Rengoku) "And, Senjuro, you're different from me! You have a big brother! And he believes in his little brother! Whatever path you walk you'll be a great person! You have a burning passion in your heart! So let's do our best! Let's work hard in life! Even if we're lonely!"
 * (To Akaza) "Growing old and dying is what gives meaning and beauty to the fleeting span of a human life. It's precisely because we age and die that our lives have value and nobility. Strength is not a word that means much in regard to the flesh."
 * (To Akaza) "I will fulfill my duty! I won't allow anyone here to die!"
 * (To Tanjiro Kamado) "Go ahead and live with your head held high. No matter how devastated you may be by your own weakness or uselessness, set your heart ablaze. Grit your teeth and look straight ahead. Even if you stop and crouch down, time won't wait for you or snuggle you and grieve along with you. Don't feel bad that I'm going to die here. As a Hashira, of course I would shield my juniors."

Reference

 * 1) https://kimetsu-no-yaiba.fandom.com/wiki/Kyojuro_Rengoku