Who Is Kokushibo? Why Michikatsu Tsugikuni Became a Demon and His Bond With His Brother Yoriichi

This article covers the Infinity Castle battle in Demon Slayer.

Who is Kokushibo?

The highest of the Twelve Kizuki: Upper Rank One.

He has six eyes and, though he’s a demon, uses Breathing techniques. With a sword style called Moon Breathing, he takes on several Hashira at once in the Infinity Castle.

Who is he really?

Michikatsu Tsugikuni, a swordsman of the Warring States period.

Michikatsu had a twin brother, Yoriichi Tsugikuni. Yoriichi was born with extraordinary talent and created Sun Breathing, the origin of every Breathing style. No matter how hard Michikatsu worked, he could never catch up.

Why did he become a demon?

He wanted time to perfect his swordsmanship.

Some swordsmen who mastered Breathing developed a Demon Slayer Mark on their bodies, making them stronger at the cost, it was said, of not living past twenty-five. When Michikatsu’s mark appeared, he panicked at how little time he had left. When Muzan appeared with an offer, he chose to become a demon, free from age and death, so he could keep perfecting his sword.

What was his relationship with Yoriichi?

For Michikatsu, Yoriichi was always a back he could never reach.

Yoriichi adored his brother, but Michikatsu never stopped envying his talent. Decades after becoming a demon, he met the aged Yoriichi again. Just as Yoriichi was about to cut him down, Yoriichi died of old age, and the fight ended unresolved. In the dead Yoriichi’s robes, Michikatsu found the flute he had given his brother when they were children.

Personally, I think Kokushibo is the demon that most directly shows the pain of standing next to someone gifted. Even as a demon, he couldn’t surpass Yoriichi. That’s the self he saw at the end.

How is he connected to Muichiro and Tanjiro?

Mist Hashira Muichiro Tokito is Michikatsu’s descendant. In the Infinity Castle, Muichiro fights his ancestor Kokushibo and dies.

The Hinokami Kagura dance passed down in Tanjiro’s family is Yoriichi’s Sun Breathing, handed down to Sumiyoshi, an ancestor of the Kamado family. The earrings Tanjiro inherited were Yoriichi’s too. That’s why Muzan was shaken when he saw them.

How did he die?

Gyomei Himejima, Sanemi Shinazugawa, Genya and Muichiro corner Kokushibo. Seeing his own hideous reflection in a blade, Kokushibo loses sight of what he had wanted to become and crumbles away. His relationship with Muzan is covered in the Muzan article.