Kyojuro Rengoku (煉れん獄ごく 杏きょう寿じゅ郎ろう, Rengoku Kyōjurō) was a supporting character in the manga series Demon Slayer: Kimetsu no Yaiba, as well as its anime adaption.
Rengoku was a Demon Slayer and the Flame Pillar of the Demon Slayer Corps, standing amongst the mighty Hashira. He would eventually die at the hands of the Demon Akaza.
He is voiced by Satoshi Hino.
Kyojuro was a young man with bright yellow hair with red streaks, black forked eyebrows, and golden eyes. He was fairly tall by Japanese standards and possessed a relatively muscular build.
His outfit consisted of the regular Demon Slayer uniform along with a white-yellow gradient pattern and red flame-like ridges at the end.
Kyojuro was greatly enthusiastic in regard to his duties as a Pillar and often cheerfully eccentric. He was amiable, kind and was almost always seen with a jovial expression. He boasted extraordinary technique and swordsmanship stemming from strict practice and discipline.
Kyojuro 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 that those who were born strong have a duty to protect the weak.
Kyojuro, along with the rest of the Pillars, was summoned to the Demon Slayer Headquarters for the semi-annual Hashira meeting and to enact a trial. The suspects in question were Tanjiro Kamado and Nezuko Kamado, the former of which was a Demon Slayer who had protected his Demon sister (Nezuko) in clear violation of the Corp's code. The Water Pillar Giyu Tomioka was also guilty of the same crime, although his penalty was set to be decided at a later date.
While Shinobu Kocho wanted to understand the reasoning behind Tanjiro's violation of the code, Rengoku, and a majority of the Pillars, simply wanted to execute Tanjiro and his sister on the spot. He respectfully voiced his disdain when Ubuyashiki decided to sanction Tanjiro's situation, and was shocked when the master revealed that Tanjiro had met Muzan Kibutsuji himself. Rengoku watched on as Sanemi Shinazugawa attempted to coax Nezuko into consuming his nutrient-rich blood, and later admired Tanjiro for ambitiously claiming that he would defeat Kibutsuji.
In the evening after the trial, Rengoku attended the Hashira Meeting. Ubuyashiki and the Hashiras mostly discussed the potency of new recruits and the plans of Kibutsuji. Rengoku expressed jealousy towards Kamado for his encounter with Lower Moon Five and that he desired to kill more of the Twelve Demon Moons.
The night after the meeting, Rengoku received word that a Demon had devoured over 40 people on a train, and that any Slayer that was dispatched met the same fate. Believing that the Demon in question could be a member of the Twelve Demon Moons, Kyojuro left Headquarters to deal with the threat.
Breath of Flames Style (炎ほのおの呼こ吸きゅう Honō no kokyū): This technique allowed Rengoku to increase the amount of oxygen in his blood by controlling his breathing pattern, which increased his strength and agility to equal that of a Demon. Kyojuro had learned to do full focus breaths at all times, further increasing his base strength, speed and stamina. By focusing his breathing on specific points, he was capable of stopping bleeding from injuries. There are at least a total of nine styles that can be used with the Breath of Flames, although Rengoku only displayed five of these.
- First Style: Sea of Fire (壱いちノ型かた 不知火しらぬい Ichi no kata: Shiranui): Kyojuro would charge towards his opponent at high speed and decapitate them in one or multiple slashes. This technique had enough force to launch train carriages off their tracks.
- Second Style: Ascending Blazing Sky (弐にノ型かた 昇のぼり炎えん天てん Ni no kata: Nobori en ten): An ascending slash. Kyojuro used this technique to slice Akaza's arm in half.
- Fourth Style: Wave of Blazing Flames (肆しノ型かた 盛せい炎えんのうねり Shi no kata: Sei en no uneri): Kyojuro span his sword in a circular motion, deflecting his enemies attacks.
- Fifth Style: Flame Tiger (伍ごノ型かた 炎えん虎こ Go no kata: Enko): A series of sword slashes that took on the form of a tiger. Kyojuro used this technique to contest Akaza's War Style.
- Ninth Style: Purgatory (玖くノ型かた 煉れん獄ごく Ku no kata: Rengoku) - A devastating dashing slash that Kyojuro initiated from a high stance, the technique had enough power to carve a deep impression in the ground where he used it. Before using this technique he remarked to himself about "thoroughly hollowing out most of the area".
- Rengoku means "purgatory" in Japanese.
- Kyojuro was ranked in 7th place as of the first character popularity poll with 1,021 votes.
- Kyojuro loved to watch sumo wrestling.
- Kyojuro's favorite food was sweet potatoes and his favorite side dish was salt grilled bream.
- Kyojuro's birthday was May 10th and he was 20 years old at the time of his death.
- Kyojuro always wanted a pet, but he has never been able to have one because of his father's hatred toward animals.
- At the time of his death Kyojuro weighed 72 Kg and was 177 centimeters (5'9½") tall.