We can often explain characters’ powers and abilities by their lineage. For example, in Demon Slayer, a popular question posed by fans is whether Tanjiro Kamado comes from a family of strong Demon Slayers from the past. In the case of this blog, is Kokushibo related to Tanjiro?
Before digging deep into the relationship between Tanjiro and Kokushibo, we need to take a quick look at their biography. This could help to find out the answer.
Who is Tanjiro?

We will only spend a little time talking about Tanjiro because he is famous. He is, after all, the main character of Demon Slayer. So instead, here are only some main points about Tanjiro.
Tanjiro was born into the Kamado family, a clan with a long tradition of selling coal. They have done this job for hundreds of years. They also have a culture of performing the Dance of Fire God every New Year.
Tanjiro followed the clan’s tradition until a demon killed his family and turned his sister into a demon. So, he learns to become a Demon Slayer to avenge his family and to turn his sister back into an ordinary human.
Who is Kokushibo?
Kokushibo is the strongest demon under the Demon King Muzan Kibutsuji. He is Upper Moon One and has been a demon for hundreds of years.
Kokushibo as a Child
When he was a human, Kokushibo‘s real name was Michikatsu Tsukugini. He was the older twin of Yoriichi Tsukugini – the legendary swordsman of the Demon Slayer Corps. Yoriichi created Sun Breathing, the origin of all modern-day breathings.
However, Kokushibo was jealous of his twin brother. While Yoriichi had the gift of God at birth, Kokushibo was only the shadow of his younger brother.
Despite being twins, the lives of Yoriichi and Kokushibo couldn’t be more different.
At first, Kokushibo was chosen to inherit all of the Tsukugini family. On the other hand, Yoriichi, because of the weird mark on his forehead, was almost killed by their father at birth.
However, their mother stopped it; instead, she convinced her husband that Yoriichi would become a monk when he turned ten. At that time, Kokushibo felt pity for his twin brother.

One day, Yoriichi saw a swordsman teaching swordsmanship to Kokushibo. That was the first time Yoriichi talked and smiled in seven years. Kokushibo felt nauseous when he saw his younger brother smile.
Kokushibo didn’t know that that day would change the fate of the two brothers forever. Yoriichi asked the swordsman if he could try the sword.
After learning some basic techniques, the brothers get into position. Yoriichi quickly breaks the wooden sword of the trainer and attacks him four times in succession: a 7-year-old kid knocked out a mature swordsman.
The person whom I had, until that moment, looked down on had far outstripped me.
Kokushibo, on seeing 7-year-old Yoriichi’s swordsmanship skills
That swordsman told that story to the father of Kokushibo and Yoriichi. After that, everything changed; the two brothers’ fates switched. Yet before that happened, Yoriichi left the house and moved to the pagoda.
Kokushibo once read the diary of his mother. He found out that Yoriichi was a genius given the gift of God, which he did not have. As a result, his feelings toward his younger brother switched from compassion to jealousy.

Kokushibo as a Demon Slayer
Yoriichi saved Kokushibo from demons many years later, and the older twin was shocked by his swordsmanship. It was perfect and touched the peak, far from younger Yoriichi.
Kokushibo gave up everything to become a Demon Slayer like his brother and became one of the strongest swordsmen then. But even then, no one can catch up to the level of Yoriichi.
He unlocked the Demon Slayer Mark and tried to learn Sun Breathing from his brother. But he could learn a small piece of Sun Breathing and instead made another version called Moon Breathing.

As other Demon Slayers who had mark died eventually, Kokushibo dwelt on anger, upset, and disappointment. No matter how he tried, he could not reach the level of Yoriichi.
The King of Demons came and promised to give him eternal life and improve his strength. Kokushibo accepted it and became the Upper Moon One of the Twelve Kizuki.
So, here is the answer to the question:
Is Kokushibo Related to Tanjiro?
They do not have any particular relationship besides enemies. Tanjiro is a Demon Slayer, and Kokushibo is a demon.
But if we dig deeper, Tanjiro might be the next generation of his younger twin. Because Yoriichi once saved the ancestor of Tanjiro, he learned to perform Sun Breathing and taught it to the next generations to remember his benefactor.

After Yoriichi died, the Kamado family learned and performed Sun Breathing (or Dance of the Fire God). And Tanjiro is the final member of the Kamado family to use Dance of Fire God.
So, Kokushibo’s feelings for Tanjiro might be different from others. After all, the boy can use the technique he spent his whole life trying to learn but couldn’t, which reminds Kokushibo of his brother. Aside from this, Kokushibo and Tanjiro don’t have a blood connection.
However, Kokushibo has a descendant in the Demon Slayer Corps.
The Next Generation of Kokushibo
Mist Hashira Muichiro Tokito is a blood relative of Kokushibo. In Chapter 165, Kokushibo met Muichiro and asked for his name. After that, the demon immediately realized their relationship.
He was quickly able to because Kokushibo could get into Transparent World. This state allows Kokushibo to see through everything, including blood and cells. Because of this, he uncovered the identity of Muichiro just by looking at the boy.

That’s about the relationship between Kokushibo and Tanjiro. He nearly does not have any relation with Tanjiro except as enemies, as Tanjiro uses a technique he couldn’t do.
The character with a blood relationship with Kokushibo is Muichiro Tokito.