Skip to main content
Evidiant
← All topics

What happened between Yoriichi and his brother?Fiction

In-universe lore. Claims are judged against the fiction's own canon, not the real world.

Yoriichi Tsugikuni and his older twin Michikatsu were born into an era that read twins as an ill omen. One of them became the swordsman every Breathing Style descends from; the other became Kokushibo, Upper Rank One of the Twelve Kizuki.

10 established, 1 disputed, 2 debunked, 1 unresolved. We do not pick an answer; the evidence places each claim. How we decide

45 citations from 8 independent sources - 37 echo the same voices and count once. Graded A1-D1.

Added 4 Aug 2026 - canon current as of 4 Aug 2026

What the four states mean
  • Establishedsupported, uncontested
  • Disputedcredible sources disagree
  • Debunkedrefuted by the evidence
  • Unresolvedno settled answer

Established 10supported, uncontested

  • Twins were held to be a bad omen when the brothers were born, but it was the large mark on Yoriichi's forehead that made their father consider having him killed; their mother's rage stopped it, and it was settled instead that Yoriichi would be sent to live in the temples at ten.▰▰▰▱▱ likely3 points
    Supports
    • During the time they were born, twins were considered a bad omen as they caused a struggle between them for succession. Additionally, Yoriichi was born with a large mark on his forehead, causing their father to consider having him killed. When their mother heard this, she became deeply enraged and grabbed him, needing to be restrained by their servants. Instead, it was decided that Yoriichi would be sent to live in the temples when he turned ten, adopting a life of priesthood.Chapter 177 - Kimetsu no Yaiba Wiki analysis
    • The father of Yoriichi was a loving husband. He gave unfair treatment to Yoriichi, the younger brother of twins who were rumored to be unlucky, after seeing his birthmark.Kimetsu no Yaiba Official Fanbook 2, Yoriichi profile: transcription and translation Word of God
    • During that time, male twins were considered to be a bad omen. Therefore, their father considered killing Yoriichi. Their mother stood heavily against this and convinced her husband to, instead of killing the baby, send him away to become a monk when he turned 10.Demon Slayer: Kokushibo's Connection to Yoriichi, Explained - Game Rant summary
  • The other Breathing Styles exist because Yoriichi could not hand his own over intact: he set out to teach his fellow Demon Slayers, none of them could match him, so he altered the styles to suit each of them personally.▰▰▰▱▱ likely3 points
    Supports
  • Michikatsu attained a mark similar to his twin's but could not use Sun Breathing, and used instead a derivative that came to be known as Moon Breathing.▰▰▰▱▱ likely3 points
    Supports
  • Two things are given as pushing Michikatsu into Muzan's offer: training had not closed the gap with his brother, and marked swordsmen were dying in droves once it was discovered the mark traded lifespan for power. The offer put to him was that he could live forever and go on mastering his Breathing Style.▰▰▰▱▱ likely4 points
    Supports
    • He had thought he could match Yoriichi's power by training, but as he languished in frustration, those who gained the mark began to die in droves. They soon discovered the mark merely exchanged a user's lifespan for the given power, and as such, what was dubbed the "Golden Era" of Demon Slayers would end; Michikatsu was subsequently left with no future or the necessary training to surpass Yoriichi.Chapter 178 - Kimetsu no Yaiba Wiki analysis
    • It was then that he encountered Muzan Kibutsuji; the Demon King tempted him by explaining he could live forever, and by doing so, he could master his Breathing Style and Muzan would gain a demonic swordsman from it. Given the choice, Michikatsu realized the path he truly sought had been laid before him, and he could be free of all his fetters.Chapter 178 - Kimetsu no Yaiba Wiki analysis
    • Chasing after Yoriichi's strength, he abandons his family and becomes a Demon Slayer, but as compensation for his mark, he is given little time to live. He chose to free himself from all ties of obligation and renounced being a human.Kimetsu no Yaiba Official Fanbook 2, Kokushibo profile: transcription and translation Word of God
    • Envious of his brother's talent, he became a demon to perfect himself as a swordsman without the fear of death.List of Demon Slayer: Kimetsu no Yaiba characters - Wikipedia analysis
  • Yoriichi did not speak until he was seven and was thought to be deaf; he struck a trainer four times in an instant where his brother had never once landed a blow, and pressed for the secret afterwards he said he had observed his opponent's skeletal alignment, muscular contractions and blood flow.▰▰▰▱▱ likely3 points
    Supports
    • However, Yoriichi never once smiled, not doing so even as an infant; furthermore, he did not speak until he was seven and was thought to be deaf.Chapter 177 - Kimetsu no Yaiba Wiki analysis
    • Yoriichi then suddenly lunged forth and struck the trainer with three quick blows, before a fourth blow knocked the man down to the ground. Michikatsu was astonished as he never once was able to land a blow, yet Yoriichi had landed four in an instant; a seven-year-old child causing a grown man to develop fist-sized welts on his neck, chest, stomach, and foot. After that, Yoriichi decided he no longer wanted to become a samurai as he was uncomfortable at the thought of striking others. Michikatsu pressed him for the secret of his strength, and eventually, Yoriichi said that before taking a strike, he observed his opponent's skeletal alignment, muscular contractions, and blood flow.Chapter 177 - Kimetsu no Yaiba Wiki analysis
    • Since he did not speak until he was seven years old, he was thought to be deaf. One day, one of his father's vassals gave him verbal instructions in swordsmanship as they were playing; he showed exceptional talent for swordsmanship, causing his father's vassal to faint.Kimetsu no Yaiba Official Fanbook 2, Yoriichi profile: transcription and translation Word of God
  • Michikatsu made his brother a flute and gave it to him behind their father's back. Decades later, having slashed Yoriichi's body in half, he found that same flute on him and kept it.▰▰▰▱▱ likely5 points
    Supports
  • Sixty years after becoming a demon Kokushibo met his brother for the last time. Yoriichi announced the strike and had already slit his throat before Kokushibo could react; Kokushibo braced for the follow-up, and it never came, because Yoriichi had died standing up with his katana impaled in the ground.▰▰▰▱▱ likely4 points
    Supports
  • Their mother's diary later told Michikatsu why his brother had gone: Yoriichi knew their father would make him the heir and send Michikatsu to the temple in his place, and ran away to spare him. What Michikatsu developed towards him despite that kind act was intense hatred and envy.▰▰▱▱▱ likely2 points
    Supports
    • It was later revealed to Michikatsu through their mother's diary that Yoriichi had known everything about their mother's illness, how it weakened her left side and Yoriichi's frequent attempts to support her and help her move around. It was also revealed that Yoriichi knew his father would make him his heir and send Michikatsu to the temple, ran away to spare his brother. Despite this kind act, Michikatsu developed an intense hatred and envy of Yoriichi for continuing to surpass him in everything and continually showing gratitude to gain seemingly nothing.Yoriichi Tsugikuni/Synopsis - Kimetsu no Yaiba Wiki analysis
    • His father had sent an envoy to the temple to retrieve him, though he was not there. Yoriichi disappeared seemingly without a trace; whether it was a landslide, a bear, or being kidnapped, his wish had come true.Chapter 178 - Kimetsu no Yaiba Wiki analysis
  • The Official Fanbook 2 profile of Yoriichi's family gives ages for both parents: the mother died of illness at twenty-four, and the father died at thirty-five.▰▰▱▱▱ likely2 points
    Supports
  • The Official Fanbook 2 profile of Kokushibo says that in spite of hating him, his most vivid memory in his lifetime was of Yoriichi, and that the wooden flute he gave Yoriichi as a child remains after his own death.▰▰▱▱▱ likely2 points
    Supports

Disputed 1credible sources disagree

  • Whether the mark's twenty-five-year limit admits an exception is argued inside the story itself: Kokushibo states that without exception the marked die before they reach twenty-five, and Gyomei answers him that he suspects there was an exception.▰▰▰▱▱ likely1 against3 points
    Supports
    Against

Debunked 2refuted by the evidence

  • A common claim is that Yoriichi held Hashira rank, argued from the fact that a word is engraved on his sword. Against it: he is described as not being a Hashira himself, the word on his katana differs from the wording carried on the Hashira's weapons, and he is said never to have been named a Hashira in any source material.Refuted byThe variations he created formed the first Water, Wind, Flame, Stone, and Thunder Breathing techniques and the best of these Demon Slayers became known as the Hashira, even though he isn't a Hashira himself.refuted3 against5 points
    The claim rested on
    • Yoriichi Tsugikuni was, indeed, a Hashira during the Sengoku Era, as was his brother, Michikatsu, before his deflection. Yoriichi was probably the Sun Hashira, and his status is proven by the fact that he was allowed to engrave something on his sword (something only Hashira can do), as well as the fact that it was confirmed that he was both banished from the Corps and stripped of his Hashira status.Demon Slayer: Was Yoriichi a Hashira? - Fiction Horizon summary
    • Yes he was what proves it is that only hashiras are allowed to engrave words on their swords, you can see some words are engraved on his sword which proves that he was a hashira.Was Yoriichi a hashira? - r/KimetsuNoYaiba summary
    Refuted by
  • One retelling credits Kokushibo with landing the final blow on Yoriichi. In the accounts of that meeting Yoriichi dies of old age on his feet, before he can finish cutting his brother's head off.Refuted byYoriichi never had the chance to cut Kokushibo's head entirely off, dying due to old age while standing up.refuted3 against4 points
    The claim rested on
    • So, who managed to land the final blow on a legend like Yoriichi? Unsurprisingly, it was his own twin brother, Michikatsu Tsugiki, who was the very first Demon Slayer to become a Demon himself.Who Killed Yoriichi? - Animevania summary
    Refuted by

Unresolved 1no settled answer

  • How Yoriichi lived so far past twenty-five while carrying the mark is put to him directly and left unanswered: Kokushibo asks how he survived, and what comes back is sympathy rather than an explanation.▰▰▱▱▱ likely2 points
    Supports
    • He had thought it to be impossible and questioned how he still lived. He began asking how he survived, given the curse of the mark supposedly killing him before the age of 25, when Yoriichi tearfully spoke and extended his sympathies towards him.Chapter 174 - Kimetsu no Yaiba Wiki analysis
    • Yoriichi was devastated by his decision to transform, whereas Kokushibo became disgusted seeing his younger twin now aged and decrepit, as well as infuriated upon realizing he defied the fate of all marked Demon Slayers by being far older than 25 years of age.Kokushibo/Synopsis - Kimetsu no Yaiba Wiki analysis

Spotted an error, or have a source to add? (tell us which claim). Missing a topic? .

demon slayeryoriichi tsugikunikokushibosun breathingdemon slayer marktwelve kizuki

Related