Kyojuro Rengoku (煉れん獄ごく 杏きょう寿じゅ郎ろう Rengoku Kyōjurō?) 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 Flame Hashira (炎えん柱ばしら En Bashira?) of the Taisho era.[3]Kyojuro was a young man of tall stature and lean-muscular build, with fair skin. He had long, somewhat messy, bright yellow hair that flares out around his face, with red streaks akin to flames along with two shoulder-length bangs, two chin-length bangs on the side of his head, and wears a messily ponytail behind his head. He had black forked eyebrows, and golden eyes that turns to red around the irises with white pupils. He was known to be charismatic and had an air of great optimism, having an enthusiastic smile plastered on his face nearly all the time. Kyojuro wore the standard Demon Slayer Corps uniform, which is black in the manga and tinted a deep brown in the anime. It consisted of a brown button-up jacket with a stand-up collar and long sleeves, featuring gold buttons and a shirt pocket on the left breast, with the kanji for Destroy (滅めつ Metsu?) engraved on the back of the uniform. Beneath the jacket, he wore a white long-sleeved collared undershirt. His uniform was fastened with a white belt at the waist and included traditional tattsuke-hakama pants of matching color. Over this, Kyojuro wore a striking haori draped on his shoulders like a cape, with a white-to-yellow gradient pattern and red flame-like ridges at the end. This haori originally belonged to his father, Shinjuro Rengoku, and was more than likely worn by him when he served as the Flame Hashira before Kyojuro inherited the role. For legwear, he wore a pair of red kyahan decorated with yellow flame motifs rising from the bottom up, brown tabi socks, and a pair of white zōri sandals with red straps. When he first joined the Demon Slayer Corps, he only wore the regular Demon Slayer uniform but as he rose up the ranks, Kyojuro started wearing a completely white haori identical to Mitsuri's before donning on his signature flame-patterned one come his ascension to Hashira.Kyojuro was greatly enthusiastic in regard to 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 have a duty to protect the weak. Kyojuro also loved his family immensely, displaying great respect and worry towards his father, Shinjuro Rengoku, despite him growing slowly more aggressive and apathetic towards Kyojuro. He was incredibly encouraging and optimistic towards his little brother, Senjuro Rengoku, believing in him and wishing him the best no matter what. This was further accentuated during his death where his final words for his father and his little brother were "take care of your body" and "follow your dreams no matter what". Kyojuro also believed that if someone lacks immense skill, their hard work towards their dreams and desire to help people doesn't count for nothing.Beneath his enthusiastic demeanor, Kyojuro was very logical and tactically intelligent, acting quickly and precisely in battle, especially when the lives of others are on the line. Kyojuro was also great in seeing talent in others, even in Nezuko Kamado, a demon that he wanted to kill beforehand, after seeing her risk her life to fight and protect others. Though he was extremely optimistic, Kyojuro did sometimes have a sense of foreboding that those he believed in might die, especially his friends who he cared deeply for. He, like most Demon Slayers, absolutely detested demons, usually because of their heinous deeds or because of their clashing moral values. Despite this, Kyojuro recognized and accepted Nezuko as a member of the Demon Slayer Corps after seeing her risk her life to protect the innocent, showing that Kyojuro was capable of not letting his hatred for demons cloud his judgement. As a Hashira of the Demon Slayer Corps, Kyojuro was a very powerful and skilled combatant.[4] Before he took his father's place, Kyojuro was already shown to be an amazing fighter. He successfully avenged the death of the 9 Demon Slayers that died to the Flute Demon by himself and later managed to singlehandedly defeat Lower Rank Two, Hairo, who even appraised his swordsmanship before he died. Moreover, his father, Shinjuro Rengoku, stated that, after he stopped teaching his son, Kyojuro trained himself to become a Hashira by learning from the guide book of the Flame Breathing style, a book which only had three volumes.[5]As another testament to his abilities, Akaza, the Upper Rank Three and one of the strongest known demons, acknowledged and praised Kyojuro's strength.[6] He even went as far as to offer to turn him 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 peak.[7] Akaza also complimented his fighting spirit, stating that it was getting close to the "Realm of the Highest".Indomitable Will: Kyojuro had an undaunted spirit and indomitable willpower, which even impressed the likes of Upper Rank Three, Akaza. Ever since he was a child, he has had a strong will and passion in himself due to his promise to his late mother.[8] Even when the Upper Rank overwhelmed him with powerful attacks, giving Kyojuro insidious wounds, he remained steadfast and resolute.[9] After Kyojuro lost an eye and had internal wounds caused by Akaza, he still persisted, vehemently expressing his unwavering will and determination, saying that he will protect the lives of the other innocent people no matter what.[10] Finally, when Akaza's fist pierced his solar plexus, it triggered a memory reminding Kyojuro of his mother again, giving him the final push to cut the Upper Rank's neck.[11] In the end, though his efforts were in vain, his incredible determination had a profound effect on Tanjiro, giving the incentive to push on no matter the turmoil he faced.[12] Keen 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.[5] Kyojuro could also master the entire Flame Breathing style just from reading 3 volumes of a book on it. During the battle against Akaza, he displayed keen judgement like after being attacked by Akaza's Destructive Death: Air Type, he realizes that he must fight at close range with he wanted to increase the chances of cutting of his head.[13] 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.[14] He also possesses great knowledge in the use of the Total Concentration Breathing (全ぜん集しゅう中ちゅうの呼こ吸きゅう Zen Shūchū no Kokyū?), knowing how to plug minor wounds and hemorrhaging and saved Tanjiro from dying of blood loss.[15] As another testament to his tactical intellect, Kyojuro could instantly read his allies' sign language at indicating the Flute Demon's abilities despite being unable to fully control their movements and execute a countermeasure before the demon's Blood Demon Art befell him. Immense Speed & Reflexes: As a Hashira, Kyojuro possessed tremendous speed and reflexes, so much so that even gifted Demon Slayers like Tanjiro and Inosuke Hashibira were unable to register his clash with Akaza, with the latter stating that he was on a different dimension. Kyojuro could even cause tremors to the ground and nearly launching a train off its tracks by running at such high speeds.[16] Moreover, Kyojuro could easily move at speeds much faster than the eye can see, decapitating demons before they can even react. His reflexes were so fast that he managed to cut Akaza's arm moments before the Upper Rank was going to hit Tanjiro. Kyojuro also managed to keep up with Akaza's high-speed techniques and incredibly swift movements, which he remarks is faster than the blink of an eye,[17] sometimes even managing to out-speed him. This surprised and impressed Akaza himself, who openly expressed his amazement over Kyojuro's skill.[18] Immense Stamina & Endurance: Kyojuro displayed superhuman stamina and endurance during his battles over the course of the series. In his battle with the Flute Demon, Kyojuro ruptured his eardrums, yet didn't flinch in the slightest, ignoring the pain and continuing to fight and win. In his battle with Hairo, he suffered dozens of severe wounds and injuries from gunshots and explosions coming from the former Lower Rank Two but continued to stall enough time for all the bombs he planted to be disarmed without showing any signs of pain or fatigue, which shocked Hairo into questioning whether the person he met in the past was really the same person he was fighting now. Furthermore, his battle against Enmu when he fused with an entire train, he was able to keep him at bay in five different train carts without tiring.[19] His incredible stamina and endurance was best displayed when he managed to keep up with Akaza, one of the strongest demons in existence, despite physically and mentally exerting himself beyond his limit and sustaining multiple irreparable and fatal wounds, like a smashed eye, shattered ribs and damaged internal organs.[20] Most impressively, he managed to keep Akaza at bay despite having his solar plexus pierced by the Upper Rank's arm.[21] Despite all of his fatal wounds, he did not once let go of his hold on Akaza in his attempt to let the dawn's light kill him, eventually forcing the demon to rip off his own arms to finally escape. Immense Strength: Having spent years of perfecting his physical prowess, Kyojuro possessed amazing physical strength, being capable of swinging his katana at speeds faster than the eye can see incessantly with faultless accuracy while engaging in combat and even sending Akaza flying an astonishing distance into a forest with a single blade swing. Kyojuro could also lift an entire train off its tracks by simply dashing forward. Even when he first became a recognized Demon Slayer, he had enough strength to instantly rupture his own eardrums by hitting his ears with his hands. Kyojuro also possessed exceptional grip strength that enabled him to hold down Akaza, one of the physically strongest characters in the series, despite having his solar plexus pierced earlier and sustaining multiple other fatal wounds, to the point which Akaza expressed his disbelief and shock over Kyojuro's strength which he describes as "unbelievable".[22]