I think I was was born with special strength for the purpose of defeating Muzan Kibutsuji. But I was lacking. In the end, I failed. Because of that, many more people will die. And that pains me.
Like his twin brother, Yoriichi is a tall and muscular man with long and spiky hair with red tips that he kept in a ponytail. However, unlike him he was slightly more slender and had shorter bangs and wavier hair than his brother. His Demon Slayer Mark was at the same place at the top of his forehead as Tanjiro, albeit lighter in color. Yoriichi is always seen with a solemn and calm look on his face, rarely showing emotion.
Yoriichi wore a red haori over an orange nagagi with a black hakama and a Nichirin Blade carried at the left side of his waist, conventional to most Demon Slayers. He sported hanafuda earrings created by his mother as charms when he was thought to be deaf; he later gave them to his friend Sumiyoshi, who then passed the earrings down to his descendants and eventually Tanjiro as well.
Yoriichi was a calm and respectful individual, wearing a solemn and reserved expression at all times, rarely showing outbreaks of emotion. Generally, Yoriichi had a matching low and serene disposition, evident when he killed demons without changing expression or when Muzan was caught off guard by his immense skill because he appeared unassuming. He was also extremely humble, seeing himself as just any other man and no one special despite his godly attributes; an example being the time he performed the Sun Breathing's forms for Suyako at her request and almost seemed embarrassed afterwards. Yoriichi was also noted by his brother to always have had faith in the future and was confident that despite the immense power of the Demon Slayers after they started using Breathing Styles, a generation would emerge that would surpass their own.
Despite being mostly nonchalant, he does experience strong emotions; he grieved the loss of Uta and their unborn child for ten straight days and was driven to tears seeing the joy Sumire showed at the simple act of being lifted up. He also smiled warmly and expressed gratitude to Sumiyoshi after his friend told him his life was not worthless and promised to preserve his Sun Breathing forms through his descendants. Yoriichi is also very kind, shown when he was on the way to fetch a midwife in the preparation of the birth of his child, he accompanied an old man he met along the way to see his fallen son.
As a child, it was shown that Yoriichi adored and idolized his older brother, Michikatsu, even declaring that he would support his brother's dream of becoming the strongest samurai in the land, and Yoriichi himself would become the second strongest. Even in his childhood, he was also extremely reserved and quiet, even being thought deaf by his family for seven years as he never spoke.
Yoriichi is shown to love his family greatly, particularly his older twin brother, evident when he kept the flute which reminded Yoriichi of his brother before he ran away from home, and kept it all the way till his death. When he met him after sixty years, the latter having embraced his new life as a demon. Yoriichi was deeply devastated and saddened by what his brother had become, expressing how heart-wrenching the sight of his brother was and even teared up. Still, he attempted to kill Michikatsu himself in order to stop him as a traitor of the Demon Slayer Corps.
Overall Abilities: Yoriichi is the strongest known Demon Slayer in the entire series and possibly the most powerful being that will ever exist, not only being born with the Demon Slayer Mark, Transparent World, Bright Red Nichirin Blade, Selfless State and knowledge of Breathing Styles but also a god-like physique and innate swordsmanship talent. As a child who has never picked up a sword before, he was able to defeat a trained sword instructor effortlessly and he was referred to as a miraculous prodigy beyond compare. After training as a Demon Slayer, Yoriichi could defeat multiple demons to where his older brother stated that he as a child couldn't even compare to him as an adult. He alone among the Demon Slayer Corps was able to corner Muzan Kibutsuji and overpowered him in an instant and had him on the verge of death until he managed to escape. Despite having avoided death, Muzan was deeply scarred by that encounter, referring to him as a monster, and even the sight of his earrings made him tremble in shock and the mere memories of Yoriichi caused the bodies of other demons who have never met him to tremble.
Shortly before his death of at least 85 years in age, he battled his older twin brother, Kokushibo who turned into a demon. Despite both his advanced age and apparent blindness, he quickly gained the upper-hand in the battle with a single move, slitting his throat before he finally died standing up, unscathed. Kokushibo himself admits that if Yoriichi launched a second swing before dying, he would have killed him while commenting Yoriichi's power was still in his prime.
Demon Slayer Mark: Yoriichi is the progenitor of the Demon Slayer Mark, being born with it, possessing the tremendous physical abilities granted by its effects all throughout his lifespan. Unlike all other marks users in his era, Yoriichi was able to defy fate and lived to about 85 years of age. It is presently unknown why Yoriichi is immune to the Mark's effects, but it's presumably because he was the first one ever to have it and born with it naturally, unlike all other mark bearers who must train to attain it.
- Bright Red Nichirin Blade: Yoriichi is the first person ever to be able to turn his Nichirin Blade into Bright Red color as he was born with the mark that presumably gave users the ability to turn their blade bright red as while. When fighting, Yoriichi can dye his black sword to bright red at will, letting him hamper the enhanced regeneration of demons, even Muzan's instant regeneration, burning him at a cellular level, leaving scars on his body for hundreds of years. It has also been noted by Muzan himself that Yoriichi's Bright Red Nichirin Blade was far more effective than those of the current generation Hashira and Tanjiro as Yoriichi could completely negate Muzan's near-absolute regeneration for a short period of time while the modern era Demon Slayers can only slow it down ever so slightly despite the fact that Muzan was in a much weaker condition because of the Anti-Kibutsuji Drug.
- Transparent World: Yoriichi has access to the Transparent World since birth, and could use it with surprising proficient, evident when he could watch for lung expansions and muscle contractions within a person and surmise when to strike them. This ability also granted him an advantage against Muzan, allowing him to find his weaknesses instantly and overwhelm him.
Extrasensory Perception: Outside of the sixth sense granted by the Transparent World which allowed him to see the inner workings of a person, Yoriichi also has extremely honed sensory abilities able to detect things outside the normal range of perception. Like most high-level Demon Slayers, Yoriichi would be able to discern the aura of demons from humans while also be able to tell the strength of his enemies at a glance. During Yoriichi's first encounter with Muzan, he could immediately tell that, by destiny, he was born into this world to defeat him. Yoriichi was also able to accurately sense Demon King's aura, which he describes as magma erupting from a volcano.
Genius Intellect: As a child prodigy, Yoriichi is extremely intelligent. Despite not speaking for most of his childhood, his first words were very clear and pronounced. He also displayed maturity beyond his age as he noticed her mother's illness and helped her all the way till her death. As another testament to his keen intellect, he could immediately use the Transparent World in combat despite never fighting before, being able to intuitively figure out that the lungs of person will expand before they attack and that he needed to watch their bone movement, muscle contraction and blood flow, which he used to his advantage instantly in the midst of battle. Even with just the knowledge of how to hold a sword properly and go into a stance, he was able to instantly overpower a trained sword instructor, causing him to go unconscious and cause many injuries all over his body. He was able to modify his Breathing Technique to suit the abilities of others by adapting them to their individual strengths. Furthermore, he was able to surmise that Muzan's weaknesses were his 12 organs and he could create an entirely new technique in that split second to overwhelm him.
Immeasurable Speed & Reflexes: Yoriichi possessed unparalleled levels of speed that surpass all other characters in the series, including that of the Demon King, shown when he was able to dodge every attack that Muzan launched at him and near-fatally injure Muzan with one move, despite the demon's own immeasurable speed and strength. . Even when Muzan divided himself into 1,800 flesh pieces to escape, Yoriichi still managed to reduce the number down to 300 in mere seconds. Later, when Yoriichi was in his 80s he could blitz Kokushibo, Muzan's strongest subordinate, nearly severing his neck instantly, despite Yoriichi telling him when he will strike. As another testament to his godlike movement speed, Yoriichi Type Zero, the robot doll modeled after him used by Demon Slayers to train, was built with 6 arms because 2 arms alone couldn't replicate Yoriichi's movements.
Immeasurable Stamina & Endurance: Even as a child, Yoriichi could run for a whole day without rest, he even remarked he didn't feel the least bit enervated. His vitality is also beyond peak-human level, being able to survive without food or water for 10 whole days when he was embracing his dead wife. Moreover, Yoriichi lived to his 80s without his power waning in the slightest, as shown when he instantly outmatched Kokushibo during their final confrontation.
Immeasurable Strength: Yoriichi possesses tremendous levels of physical strength possibly beyond that of nearly all other Demon Slayers in existence. As a child, he could knock out a grown man with inclined physical abilities with a wooden blade, even causing extremely severe bruises the size of fists. When he was an adult, he was able to effortlessly slice off the neck of Muzan Kibutsuji, the most fortified body part of the strongest demon in existence.
Selfless State: During their confrontation, Muzan noted that Yoriichi emanated absolutely no sense of drive, hatred, anger, fighting spirit, animosity or even bloodlust despite being in mid-battle against him, rendering it practically impossible for Muzan to detect him, predict his movements or gauge how powerful he was with his senses. This gave Yoriichi an edge in battle against Muzan as he underestimated his strength, a mistake that shook the Demon King to this day.
Unparalleled Swordsman: Yoriichi is the greatest swordsman in the series and of all time. Even as a child with no training, he was capable of easily defeating a trained swordsman the very first time he ever picked up a sword, striking him in multiple areas across his body faster than the eye can process. His swordsmanship was so tremendous that a battle doll modelled after him had to be made with 6 arms wielding katanas and utilizing 108 techniques to even attempt to imitate Yoriichi's skills, and even then, the doll was still vastly inferior compared to him. His swordsmanship easily overwhelmed the Demon King, Muzan Kibutsuji and he would have killed his twin brother, Kokushibo, the strongest swordsman in the current era, if he didn't die of old age.
Sun Breathing (
- Clear Blue Sky (
碧 羅の 天Heki-ra no Ten?) - The user spins their body vertically to deliver a 360° slash.
- Raging Sun (
烈 日 紅 鏡Retsujitsu Kōkyō?) - The user unleashes two horizontal slashes to hit or defend from incoming attacks.
- Burning Bones, Summer Sun (
灼 骨 炎 陽Shakkotsu En'yō?) - The user unleashes a large circular slash that defends from imminent frontal attacks.
- Setting Sun Transformation (
斜 陽 転 身Shayō Tenshin?) The user backflips into the air to deliver a powerful upended sword slash.
- Solar Heat Haze (
飛 輪 陽 炎Hirin Kagerō?) - The user charges towards the target, unleashing a horizontal slash seemingly covered in haze that fails to land, but actually does hit the target.
- Beneficent Radiance (
輝 輝 恩 光Kiki Onkō?) - The user spirals into the air and delivers a powerful slash that surrounds the enemy.
- Sunflower Thrust (
陽 華 突Yōkatotsu?) - The user unleashes a single thrust attack with the point of the blade.
- Dragon Sun Halo Head Dance (
日 暈の 龍・ 頭 舞い Nichiun no Ryū Kaburimai?) - The user unleashes a continuous fast and powerful sword attack that seemingly takes the form of a flaming sun dragon. This technique is capable of decapitating multiple enemies at once.
- Fire Wheel (
火 車Kasha?) - The user leaps behind the opponent and spins in the air downward, releasing a sword attack in a circular motion.
- Fake Rainbow (
幻 日 虹Gen'nichi Kō?) - The user performs high-speed twists and rotations, thus creating afterimages used mostly to evade attacks. The afterimages work most effectively on enemies with good vision.
- Flame Dance (
炎 舞Enbu?) - A two-combo strike which starts with a vertical slash and then a horizontal one right after.
- Thirteenth Form (
拾 参ノ 型Jū San no kata?) - The user continuously performs all twelve forms of Sun Breathing in repetitive succession to increase the accuracy and agility of his movements while reducing fatigue. This form was created solely for the purpose of killing Muzan, since the repetition of all twelve forms aims to destroy Muzan's twelve vital organs (seven hearts and five brains) that move freely inside his body thanks to his shape-shifting ability.
Standard Nichirin Katana: As a Demon Slayer, Yoriichi carries around a standard sized and shaped Nichirin katana that is deep black in color, but changes bright red during combat. His katana's hilt is circular shaped with 4 slight indentations, with a black center and a golden border. Yoriichi's katana also has the words Destroy (
- Yoriichi's family name is composed of the kanji for "to inherit, succeed" (継 tsugi?) and "country" (国 kuni?), while his first name means "destiny" (縁 yori?) and the old variation of the kanji for "one" (壱 ichi?).
- The bag in which Yoriichi carried his brother's flute seemed to have been made of the cloth from Uta, his late wife's kimono, due to the similar patterns.
- The relationship between Yoriichi and Michikatsu parallels the mythology of the Shintō deities Amaterasu and Tsukuyomi, respectively. Amaterasu is the most sacred of Shinto 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.
- Yoriichi's first words to his family were "I can hear you" as they believed he was deaf, up until that point.
- It is hinted that he and his wife reincarnated in the future as a very happy couple with kids.
- (To Sumiyoshi) "Sumiyoshi... those who master their trade all arrive at the same place. Even if the times change or the way to that place changes they are certain to reach the same place. You seem to think I'm someone that's special but I'm not. I cannot protect anything that's important to me and I was unable to accomplish even one thing that I should have in this life. I am a man without any value."
- (To Kokushibo) "My brother... we are not that great. We are merely a fragment of humankind's long, long history. At this moment, those whose talent will surpass ours are uttering their first cries. They may come to reach the same place. There is no need to worry. We can draw the curtain of life closed without unease at any time. Does that not exhilarate you? Brother? Someday... the children now being born will surpass us an ascend... to even greater heights."
- (To Kokushibo) "My brother, is your dream to become the strongest samurai in the land? I want to be like you. I... want to become the second strongest samurai."
- "My dream was to live a quiet life with my family in a small house where we would sleep side by side. I would be close enough to see the beloved faces of my wife and child and close enough to reach out and take their hands. That would have been enough. But even that... did not come true. (Because) demons exist in this beautiful world."
- "The Demon Slayers defeated demons, one after the next. When demons killed my elder brother's subordinates, he too became a Demon Slayer and lent us his strength. Soon after, I found the demon's progenitor. And in that moment... I knew that I had been born for the purpose of defeating him."
- (To Muzan) "What is the value of a life to you?"
- (To Sumiyoshi) "I think I was was born with special strength for the purpose of defeating Muzan Kibutsuji. But I was lacking. In the end, I failed. Because of that, many more people will die. And that pains me."