The following contains spoilers from the Demon Slayer: Kimetsu no Yaiba manga and anime.
Demon Slayershave been fightinga seemingly endless war with demons for over a millennium. Despite having the disadvantage of a fragile body while facing superhuman monsters, these brave warriors have put their lives on the line for generations.
But everything changed in the Sengoku era as Yoriichi helped Demon Slayer gainthe Demon Slayer Mark. The mysterious marking gave the swordsman a chance to win against even some of the most powerful demons in existence. Although the Demon Slayer Mark is considered the biggest blessing for a swordsman, the Infinity Castle trilogy is all set to reveal a demon who can also use the mark, in some cases, much better than the Demon Slayers themselves.
The Demon Who Can Use the Demon Slayer Mark
Kokushibo is the Only Demon With the Mark
The Demon Slayer Mark has always been a mysterious power that only a few swordsmen have been able to access. In the Taisho Era, it was Tanjiro who first awakened it,following which Muichiro Tokitoand Mitsuri Kanroji have been able to manifest it as well. However, the mysterious marking first came into existence during the Sengoku Era when legendary swordsman Yoriichi Tsugikuni was born with it.
I will stop your bleeding. Humans are so fragile. However… if you bleed to death… or if his lordship doesn’t approve of you… and you die… then death was always your fate. In that case… you were no greater a man than that. Don’t you… agree? ~ Kokushibo to Muichiro
The Demon Slayer Mark has been a unique capability accessible only to members of the Demon Slayer Corps ever since. But there is one exception. Fans may have noticedthat Upper Moon One, Kokushibo, has the Demon Slayer Mark as well. Interestingly, he is quite adept at using it and understands its applications quite intimately.
In the Infinity Castle arc, when Kokushibo faced Sanemi, Genya, Muichiro, and Gyomei, he accessed the Transparent World on quite a few occasions. This supernatural ocular ability allows the user to see through a person as if their skin were transparent. Only people with the Demon Slayer Mark can access the Transparent World.
Using this unique technique, Kokushibo was able tofigure out that Genya consumes demonsand Muichiro is his ancestor. Furthermore, he also figured out each demon slayer’s strengths and weaknesses to exploit them as the fight got more intense. But why and how does a demon have the mysterious marking? This question must have puzzled fans for a while.
Kokushibo’s Origins: How Can the Upper Moon One Use the Mark?
Kokushibo Was Once a Swordsman Back in the Sengoku Era
Upper Rank One is one of the oldest demons alive. He joined Muzan’s forces back in the Sengoku era. Before becoming a demon, he used to be an exceptional swordsman affiliatedwith the Demon Slayer Corps. He was lucky enough to be born just in time to experience the Golden Age of Demon Slayers. He awakened the mark, but soon came to realize that every swordsman who manifests it dies before the age of 25.
Driven by a ruthless desire to get stronger and to cheat death, the demon slayer accepted Muzan’s offer to become a demon. His wish was fulfilled as he no longer had to fear dying sooner and had more than enough time to refine his swordsmanship to surpass every person ever born.
Although the Demon Slayer turned into Kokushibo,the Demon Slayer Mark remained. Thus, the Upper Moon One became the only demon in existence with the mark. Kokushibo, over time, understood its applications better than anyone alive and started using it to his advantage whenever he fought. By the time the full-scale war broke out between the Demon Slayer Corps and Muzan’s forces, Kokushibo could access the Transparent World effortlessly.
As the Demon Slayer Corps faces the Upper Rank One in the Infinity Castle, they will not only find a demon, but also a master swordsman who is better than them in almost every aspect. Kokushibo’s exceptional use of the mark will only make life difficult for the demon slayers. As if this were already not bad enough, the Upper Mooncan also use Blood Demon Art, making it extremely hard to put him down.
Demon Slayer: Infinity Castle trilogy’s first installment is scheduled to be released in the United States onSeptember 12, 2025.
