Demon Slayer: Who Is Kokushibo And Why Did He Become A Demon? Explored

Kokushibo is one of the most intriguing characters in the Demon Slayer saga. But what are his origins and why did he choose to become a demon? Learn more here.

Published on Apr 01, 2024  |  12:55 PM IST |  28.4K
Exploring How And Why Kokushibo Became A Demon In Demon Slayer
Kokushibo in Demon Slayer Anime (PC: IMDb)

This article contains spoilers for the Demon Slayer manga

The fearsome demon Kokushibo in Demon Slayer is easily one of the most powerful demons to exist in the entire franchise. A remarkable swordsman, his history with the Demon Slayer Corps is also unique. But what makes the Upper Moon One different from most of the other demons in the franchise is his reason for becoming a demon after what he used to be in his human life. Unlike sibling duo Daki and Gyutaro and the Upper Moon Two Akaza, Kokushibo’s backstory induces more fear and anger than pity.

Who is Kokushibo? 

If you have not read the Demon Slayer manga yet, then you might not know the history behind the Upper Moon One ranked demon known as Kokushibo. In his human life, Kokushibo’s actual name was Michikatsu Tsugikuni, the older twin brother of the legendary Demon Slayer, the inventor of breathing styles, and the original Sun Breathing user, Yoriichi Tsugikuni, who was alive during the Sengoku era. 

The lives of the Tsugikuni brothers were unique to say the least. As a child, Michikatsu was preferred by his father over his younger twin brother as Yoriichi had a birthmark on his face which deemed him less worthy in his father’s eyes. While Michikatsu received the best of everything from comfort to even training from the best swordsman, Yoriichi only watched him from afar. But in a twist of fate, everyone discovered that Yoriichi was a much more talented swordsman than his older brother even without ever having any proper training. After the discovery of his prodigal genius, everyone’s focus shifted towards Yoriichi, Michikatsu was ignored and started to feel jealousy. 


After the rise of the demons thanks to Muzan, Yoriichi decided to start the Demon Slayer Corps to kill demons, and Michikatsu, being a great swordsman himself, joined his brother. However, he found his brother’s Sun Breathing technique too hard and started to feel even more jealous of him. He did come up with a breathing technique of his own known as Moon Breathing, which was a derivative of the Sun Breathing. 

Soon after, Michikatsu also received his Demon Slayer mark, the appearance of which scared him as it is said that the receivers of these marks only live to be 25. Due to his fear and him never being able to surpass his brother, Michikatsu decided to become a demon named Kokushibo and achieve immortality. He joined Muzan and his unique abilities as a Demon Slayer combined with his power as a demon earned him the highest rank of the Twelve Kizuki, the Upper Moon One.

Kokushibo as a demon is terrifyingly powerful 

Kokushibo is a unique demon, as he is the only one of the Upper Moons who also has experience as a Demon Slayer and even had his own unique breathing style. He also developed a demon slayer mark as a human which means even as a human he was extremely powerful and the culmination of demon powers only makes him fearsome. 

Kokushibo’s demon power allows him to see through the skin of his opponents and identify their muscle movements, blood flow, etc. This is how he was able to tell that Genya feeds on demon flesh to gain strength and that Muichiro Tokito was a descendant of himself and Yoriichi. It also allows him to correctly predict the movements of his opponents, making his moves almost impenetrable. He also has a special sword which weilds the same powers as the slayers' Nichirin blades and can be easily mended by Kokushibo mid-battle. Paired with his master swordsmanship, his powers makes him one of the most powerful opponents the Demon Slayer corps had ever faced. 

However, even with such insurmountable power, Kokushibo was never able to defeat his younger twin when he was alive. The last time those two fought, Yoriichi was an 80 year old man. And yet, the only reason Kokushibo made it out of that battle alive was because his brother died of old age while delivering the final and lethal blow to his body. Even in his death, he was more powerful than Kokushibo, a fact that haunted him until his own death in the last part of the manga. 


Michikatsu became the fearsome demon Kokushibo due to not only his fear of death, but also because of his jealousy towards his prodigal brother. He hoped that after gaining the powers of a demon, he would be stronger than his brother, something he was never able to do as a human. However, even after becoming a demon, he was not able to defeat his brother who loved him unconditionally all throughout his life.

ALSO READ: Demon Slayer: What Is The Meaning Behind Different Colors Of Nichirin Swords? EXPLAINED

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About The Author

Gargi has a Masters degree in English Literature from The University of Calcutta. She has been a content writer



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