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 the story’s greatest battle wasn’t that one. The most thrilling battle in Demon Slayer took place many years before the main plot when Yoriichi Tsugikuni, the most potent Demon Slayer, faced off against Muzan Kibutsuji, the most potent demon. At the time, Muzan was believed to be untouchable, but when he encountered Yoriichi, he not only experienced dread for the first time and nearly lost his life. This article will give you an overview of what happened during that battle and why Yoriichi actually failed to kill the Demon Progenitor when he had the chance.
Yoriichi Tsugikuni was, as the most powerful Demon Slayer, able to surprise Muzan and show him that he could be killed, i.e., that he was able to kill him. Yet, while Yoriichi did slice up Muzan, Muzan split his body into 1,800 fragments, surprising Yoriichi. The Demon Slayer reacted, but he was able to destroy only 1,500 of them, allowing the remaining 300 to flee and regenerate later. And that is why Yoriichi did not kill Muzan.
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 fight against Muzan Kibutsuji, the Demon Progenitor. 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.
Muzan used a trick to avoid being killed – and it succeeded (unfortunately)
Now, just as it was in Tanjiro’s case, Yoriichi had a very personal grudge against Muzan. In Tanjiro’s case, though, it was direct, as Muzan was directly responsible for the massacre of his family and Nezuko becoming a Demon, but in Yoriichi’s case, the fact that Muzan even existed and that he was able to turn people into Demons was what directly led to Yoriichi’s personal tragedy. So, what happened?
Yoriichi was born during the Sengoku era as the younger twin of Michikatsu Tsugikuni; due to his Demon Slayer Mark, he was viewed as strange during his childhood. He had a strained relationship with his brother, who was envious of him, but after the death of their mother, Yoriichi left the family house so that Michikatsu would not be sent to a shrine, deciding to go 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.
Later, Uta would become expecting their child. Yoriichi left the house to call for a midwife just as Uta was ready to give birth, but when he ultimately came back, he found that a demon had killed Uta and the unborn child by the time the sun had set. This shocked him so much that he stood there, holding her corpse, for ten days until a traveling Demon Slayer approached him and urged him to bury his wife.
After the catastrophe, Yoriichi took back his sword and started his demon-slaying training. Due to his prowess and possession of the Demon Slayer Mark, he eventually enlisted in the Demon Slayer Corps. He created the Sun Breathing, the first breathing technique in human history. Even today, Sun Breathing is the most potent and difficult-to-learn Breathing Style. All other breathing techniques, such as Michikatsu’s Moon Breathing, which Yoriichi’s brother created since he could not master Sun Breathing, were descended from Sun Breathing.
Yoriichi was granted the right to personalize his katana once he attained the highest rank of Hashira, the most powerful one, as all Hashira are. Then he went after Demons once more. Yoriichi soon encountered Muzan Kibutsuji, the ancestral demon and mortal enemy of the Slayers, and decided to kill him because he knew that while Muzan did not physically kill his wife and kid, he did create the demon that did. Yoriichi was determined to murder Muzan because he believed doing so would end the Demons.
Muzan wasn’t impressed because he had killed many Demon Slayers before Yoriichi, but he soon sensed that Yoriichi was unique and knew that Yoriichi could kill him if given a chance. Muzan was able to avoid Yoriichi’s attacks, but he was aware that if he hadn’t done so, they would have killed him. When Yoriichi entered the Transparent World, he saw that Muzan had a total of seven hearts and five brains, which moved around inside his body. Yoriichi then concentrated his Sun Breathing Style into one attack, using it to slice Muzan, who was shocked and fighting for his life.
Then, to Yoriichi’s surprise, he scattered his body into 1,800 smaller fragments. Despite acting quickly, the Demon Slayer could only destroy 1,500 of the 1,800 fragments, allowing the other 300 to escape and later regenerate. This is exactly what occurred, but Muzan was terrified of Yoriichi afterward and hid for a long(er) length of time rather than confront Yoriichi again.
And that is how Muzan actually survived. It is not that Yoriichi did not want to kill Muzan – it was his main goal – but Muzan simply used a cheap trick, and Yoriichi was unable to completely eliminate these fragments. Yoriichi would regret this failure for the rest of his life, considering himself directly at fault for Muzan’s future bloodshed, as he was the one who had the opportunity to kill him but failed to do so.