Your sister must never take the life of an innocent person!
Sakonji Urokodaki (
Sakonji's face has never once been revealed or depicted throughout the entire completed manga; he is always seen wearing a tengu mask that covers his entire face although Tanjiro states through a Taisho secret that Sakonji's face is very gentle and calm. He appears to be an elderly individual, as noted by the countless number of students he's trained, along with his silver-colored hair. In his youth, his hair was black and fashioned into a topknot.
He is always seen wearing a cloud-patterned jinbei kimono with navy colored pants which are fastened at his shins by white kyahan guards. He also wears traditional black tabi socks, and sandals similar to Tanjiro, except his sandals have blue straps. On the occasions when Sakonji travels, he wears a white cloth that covers his head and wraps around his neck.
While seeming at first like a stern, grouchy old man, this hides an extremely compassionate personality. Though he pushes his students hard, he also cares for them deeply, viewing them as akin to family, and is one of the few Demon Slayer Corps characters to wholly trust Nezuko to never eat a human. Similarly, he wholly trusts that Tanjiro will find a way to restore her humanity.
Not much is known about Sakonji's past, however he was a Demon Slayer in his youth, and was also the one responsible for capturing the Hand Demon. He would then go on to become the Water Hashira for an undisclosed period of time, before retiring to become one of the cultivators of Water Breathing swordsmen.
Having received a letter from Giyu Tomioka requesting that he train Tanjiro Kamado, which also explained the boy and his sister's circumstances, Sakonji set forth from his home to find the two. Upon finding them, he stops Tanjiro from attempting to kill a Demon with his knife, stating that the boy will be unable to kill the creature with such a blunt weapon. Admonishing the youth for his question of how to properly defeat the beast, the elder watches as Tanjiro struggles to come up with a way to dispatch the creature. Sniffing the youth, Sakonji determines that he is no good, as he still has the scent of kindness even when confronted by vile demons.
While Tanjiro is still struggling to kill the demon, Sakonji buries the victims of the creature, afterwards kneeling by their graves with his hands together in prayer. He then introduces himself to the youth, asking if he is the one Giyu spoke of in his letter. Getting an affirmation to his inquiry, Sakonji goes on to ask the boy what he will do if his sister decides to feast on a human, slapping him when he hesitates to answer. He admonishes the youth on his slowness to answer, stating that he lacks determination, and stresses that he must not allow his sister to harm another human under any circumstance. Getting an answer of conviction from Tanjiro, the elder agrees to test the boy to see if he is worthy of becoming a Demon Slayer, telling him to bring his sister and follow him.
Sakonji then swiftly makes for his home, with Tanjiro struggling to keep up with his pace. Arriving at their destination, the elder tells the exhausted youth that the test begins now, instructing him to hike up the mountain. He travels with the boy part way up the mountain, telling him that he must make his way back to his home before dawn. He then vanishes into the heavy fog surrounding them. Later, having made his way back down the mountain, Sakonji drapes a blanket over Nezuko, before noticing a noise at his door. A heavily exhausted and injured Tanjiro opens the door, prompting the elder to recognize his abilities, and thus his passing of the test.
Sakonji explains his profession as a Cultivator to Tanjiro, as well as how to join the Demon Slayer Corps: surviving the Final Selection. To prepare him for this trial, and to see if he is worthy of even being able to participate in it, Sakonji begins to train Tanjiro in the way of the sword. He explains the intricacies of the weapon and the forces behind it, sparring with Tanjiro to improve his endurance using only his bare hands. Alongside this, he trains the boy in proper breathing techniques, slapping his stomach when he fails to get it right.
When Nezuko falls into a coma, Sakonji calls for a doctor, who cannot find anything wrong with her. Finally, after a year has passed, the elder tells Tanjiro that he has nothing more to teach him, instructing him to prove himself by improving the basics he has been taught. He then leads the youth to a huge boulder, telling him that if he can cut it in half, he will be permitted to go to the Final Selection. When Tanjiro hesitates, overcome by doubt, Sakonji leaves without a word, his hand in the boy's training completed.
Much later, after Tanjiro finally succeeds in slicing the boulder in half, Sakonji explains his reasons for not wanting Tanjiro to go to the Final Selection, complimenting the youth on his accomplishment. He then wraps the youth in a hug, urging him to come back alive from the Demon Killing Corps' test. Before Tanjiro leaves, the elder cuts his hair and gives him a mask to ward off bad luck. Besides, Sakonji explains that Demons increase in power by consuming humans, can use a type of sorcery to alter their bodies and that Tanjiro will be able to figure out how many humans a Demon has consumed if he increases the sensitivity of his nose. When Tanjiro wishes him farewell, asking the old man to look after Sabito and Makomo, Sakonji wonders aloud how the boy knew the names of his two dead apprentices.
After Tanjiro returns from the Final Selection, Sakonji and Nezuko embrace him, the elder weeping tears of joy while saying that the youth had finally made it back alive. Fifteen days after this, Haganezuka arrives with Tanjiro's new sword, but ignores the youth's attempts at hospitality, prompting Sakonji to note to himself that the swordsmith hadn't changed. He then agrees with Haganezuka when he notes that Tanjiro's blade may turn red, watching shortly after that as it instead turns black. Noting this, the elder watches as Haganezuka throws a fit over this unexpected development.
Sakonji then watches in silence as Tanjiro buttons up his uniform, and subsequently shows him a box made out of "Mist Cloud Fir", which he can hide Nezuko from the sun with. He speculates that Tanjiro's sister may have fallen into her coma because she was attempting to regain strength through sleep, rather than through consuming humans. He goes on to tell Tanjiro that while she was sleeping, he gave Nezuko some suggestions to her subconscious to defend humans as her family from other demons. He also informs his apprentice about Caster Demons and the monster responsible for the creation of other Demons and the murder of Tanjiro's family, Muzan Kibutsuji.
After Nezuko's existence was discovered by the Demon Slayer Corps, Sakonji sends a letter to Kagaya Ubuyashiki. In it, he requested Tanjiro Kamado be forgiven for harboring a Demon and explained Nezuko's unique circumstances. He further wrote that if Nezuko were to ever kill a human he, Tanjiro, and Giyu will all commit Seppuku to repent.
While Tanjiro and the remaining Hashira engaged Muzan and the remaining Kizuki in the Infinity Castle, Sakonji was summoned to the Butterfly Mansion to protect Nezuko, who's newfound resistance to sunlight Muzan now seeks. He also gave her the cure developed by Tamayo, which would turn her back into a human and thus ruin Muzan's plans. While tending to her as she fell ill as a result of taking the cure, Sakonji thought about everything that happened since he met her and Tanjiro and told both of them not to lose.
- Enhanced Sense of Smell: Sakonji has a heightened sense of smell which allows him to sense the 'line of interval'—the slight pause in an enemy's movement which allows an opening to strike—and distinguish between species, as well as their approximate position. This is revealed when Giyu Tomioka writes to Sakonji, asking for him to train Tanjiro citing that he also possess the same ability as the cultivator. This was further shown during his first meeting with Tanjiro during his battle against the Temple Demon, where Urokodaki was able to smell out Tanjiro's emotions and smell "the scent of innate Kindness" from him.
Water Breathing (
- First Form: Water Surface Slash (
壱ノ 型 水 面 斬り Ichi no kata: Minamo Giri?) - The swordsman generates enough momentum to create a powerful single concentrated slash.
- Second Form: Water Wheel (
弐ノ 型 水 車Ni no kata: Mizu Guruma?) - The swordsman leaps and vertically spins forward in the air while releasing a flowing attack in a circular motion.
- Third Form: Flowing Dance (
参ノ 型 流 流 舞い San no kata: Ryūryū Mai?)  - The swordsman swings his blade at his opponent in a way that mimics the movement of waves on the surface of water.
- Fourth Form: Striking Tide (
肆ノ 型 打ち 潮Shi no kata: Uchishio?) - The swordsman makes multiple consecutive slashes while twisting their body in a flowing fashion similar to a harsh tide.
- Fifth Form: Blessed Rain After the Drought (
伍ノ 型 干 天の 慈 雨Go no kata: Kanten no Jiu?) - A "sword strike of kindness" that kills the target with little to no pain. Used when the enemy surrenders.
- Sixth Form: Whirlpool (
陸ノ 型ねじれ 渦Roku no kata: Nejire Uzu?) - The swordsman fiercely twists his upper and lower body, creating a whirlpool that cuts anything caught in it. It can be used in a place without footing, and if used underwater can generate a large whirlpool that draws in anything nearby in addition to cutting them up like a large blade.
- Seventh Form: Drop Ripple Thrust (
漆ノ 型 雫 波 紋 突き Shichi no kata: Shizuku Hamon Tsuki?) - A fast and accurate stab. The fastest Breath of Water technique.
- Eighth Form: Waterfall Basin (
捌ノ 型 滝 壼Hachi no kata: Takitsubo?)  - The swordsman cuts the target vertically.
- Ninth Form: Splashing Water Flow (
玖ノ 型 水 流 飛沫Ku no kata: Suiryū Shibuki?) - Minimizes the landing time and surface needed when landing, allowing the user to move without limits. Ideal when fighting in a place with no solid foothold.
- Tenth Form: Constant Flux (
拾ノ 型 生 生 流 転Jū no kata: Seisei Ruten?) - A continuous attack that increases in power with each rotation, creating a strong slash.
- Sakonji was ranked in 14th place as of the first character popularity poll with 213 votes.
- It is said by Giyu in his letter to Sakonji that he has an enhanced sense of smell like Tanjiro.
- Sakonji doesn't drink alcohol and has a very low alcohol tolerance.
- Sakonji started wearing his mask because Demons used to make fun of his gentle face.
- (To Tanjiro Kamado about Nezuko) "Your sister must never take the life of an innocent person!"
- (To himself regarding Tanjiro and Nezuko Kamado) "Tanjiro... when I think about it, ever since you brought your younger sister, who had become a demon I've felt as thought large cogs have been turning. If this war is a giant machine then when the two cogs that are you and Nezuko fitted into place, it caused a stagnant situation to suddenly begin moving. Don't lose, Nezuko. Don't lose, Tanjiro. You must not lose."