Demon Slayer: Here’s Why Yoriichi Didn’t Kill Muzan & Why He Regrets It!

In terms of Demon Slayer, the best-known and most important fight was between Tanjiro and Muzan, of course, which ended the story on a very epic note. But that wasn’t actually the most epic fight in the story. The most epic fight in Demon Slayer happened many years before the main storyline, when the most powerful demon, Muzan Kibutsuji, fought the most powerful Demon Slayer, Yoriichi Tsugikuni. Now, Muzan was thought to be invincible at the time, but when he faced Yoriichi, not only did he sense fear for the first time, he almost died in the fight as well. In this article, we are going to tell you how Muzan survived his fight against Yoriichi and why Yoriichi regretted it until the day he died.

Yoriichi Tsugikuni was able to defeat Muzan, but before he was able to kill him, Muzan’s body split into 1,800 small pieces, and Yoriichi managed to destroy only 1,500 of them, allowing the remaining 300 to flee and regenerate. He regretted his failure to kill Muzan for the rest of his life because Muzan being alive meant that his bloodshed would continue.

The remainder of this article will give you a detailed overview of Yoriichi Tsugikuni’s story, as it happened on the pages of the Demon Slayer: Kimetsu no Yaiba manga, especially in relation to his fateful duel against Muzan Kibutsuji. You already know what happened and how it happened, so we will just bring you the details so you know the whole context. Be careful, though, as the article will contain many spoilers, so if you don’t know all the details, be careful how you approach the text.

Yoriichi wanted to kill Muzan because a Demon killed his wife and unborn child

Originally from the Heian era, Muzan was a sickly young man whose transformation into a demon resulted from experimental therapy to extend his life. Before realizing he was at work, he killed his doctor. Since then, Muzan has dedicated himself to “finishing his therapy” by utilizing demons to help him accomplish his objective of being without flaws—the sun being his one weakness. Since he had a close call to death during his battle with Yoriichi Tsugikuni, he also voiced legitimate concern for individuals using the Sun Breathing technique.

Yoriichi, on the other hand, was born later, during the Sengoku era. After a troublesome childhood, he left his family home after the death of his mothers, going into the mountains. Yoriichi had been running nonstop for a day and a night without showing any signs of tiredness when he came upon Uta, a young woman his own age whose entire family had perished. Yoriichi decided to reside with her, and after ten years, Uta and Yoriichi were wed.

Uta would later become pregnant with their child. Just before she was about to give birth, Yoriichi left the house to summon a midwife just before the expected arrival time, but when he eventually returned home, he discovered that Uta and the unborn child had been murdered by a demon by the time the sun had set.

Yoriichi was so horrified by the catastrophe that he kept her body in his arms for ten days straight before finally burying them at a Demon Slayer’s urging. As a result, Yoriichi decided to reclaim his sword and begin his training to slay demons. He would soon join the Demon Slayer Corps and, being so skilled and a possessor of the Demon Slayer Mark. He developed the first Breathing Style in history, the Sun Breathing. Sun Breathing remains, until today, the most powerful Breathing Style and the most complex one to master. All the other breathing styles were derived from Sun Breathing, including Michikatsu’s Moon Breathing, which Yoriichi’s brother developed because he was unable to master Sun Breathing.

After becoming a Hashira, the most powerful one, Yoriichi was allowed to engrave something on his katana, as all Hashira are allowed to. He then continued his pursuit of Demons. Yoriichi soon came into contact with Muzan Kibutsuji, the Slayers’ mortal foe and ancestral demon, and made the decision to murder him, knowing that while Muzan personally did not kill his wife and child, he created the demon who did it. Yoriichi knew that killing Muzan would bring an end to the Demons, which is why he was intent on doing it.

Muzan wasn’t impressed, as he had killed numerous Demon Slayers before Yoriichi, but he soon felt that Yoriichi was special and knew, somewhere, that Yoriichi would be able to kill him if given a chance; he was able to dodge his attacks but he knew then that these attacks would have killed him had he not dodged them. Entering the Transparent World, Yoriichi observed that Muzan had a total of seven hearts and five brains that change position within his body, so he focused his Sun Breathing Style in one attack and used the attack to slice Muzan, who was shocked and struggling to remain alive.

He then dispersed his body into 1,800 smaller pieces, which surprised Yoriichi. The Demon Slayer reacted swiftly, but he was able to destroy only 1,500 of the 1,800 fragments, thus allowing the remaining 300 to flee and regenerate later on. And this is exactly what happened, but Muzan was, since then, afraid of Yoriichi and hid for a long(er) period of time because he did not want to face Yoriichi again.

Failing to kill Muzan was Yoriichi’s biggest regret

After failing to kill Muzan, he met Tamayo, another demon, and believed her story about wanting to end Muzan, so he let her go free. Upon his return to the Corps, he found out that his brother, Michikatsu, had betrayed the Corps, killed the Oyakata, and deflected. Being blamed by the other Hashira, Yoriichi was initially sentenced to death for his failures, but the new Oyakata converted the death sentence to banishment.

And so, Yoriichi was stripped of his Hashira rank and banished from the Corps. After his banishment, Yoriichi went to Sumiyoshi’s to enjoy their company and because he needed someone to talk to. Yoriichi got unhappy as he reflected on the misfortunes that had befallen him and expressed remorse for having left Muzan alive when they first met, as well as the countless deaths that would occur. This was his biggest failure, one he regretted until his death.