The following contains spoilers from the Demon Slayer: Kimetsu no Yaiba manga or anime.
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Demon Slayer: Kimetsu no Yaibais all set to adapt its most exciting arc in the Infinity Castle trilogy. The storyline features some of the most intense battles in the series so far and is expected to reveal bizarre secrets that will prompt fans to reconsider their preconceived notions.
The trailer has already set the tone for a few exciting battles ahead that will reshape the final showdown with Muzan in unimaginable ways. Although all of these battles are consequential, Zenitsu’s rivalry with Kaigaku has drawn the attention of the fans because of its unique nature. So what makes this particular fight so exciting, and why could it potentially be thebest one in the Infinity Castle? Let’s try to understand.
The Roots of a Bitter Rivalry
Bullying, Lies, and Betrayal
Zenitsu and Kaigaku were once mentees of theformer Thunder Hashira, Jigoro Kuwajima. Although the exceptional swordsman was kind enough to treat everyone equally and tried to instill the same values in his pupil, he could not do much to change Kaigaku’s nature. The talented young trainee used to bully Zenitsu relentlessly and was quite cruel to him. Agatsuma never took a stand for himself because of his low self-esteem, and eventually forgot about his bully once he became a demon slayer.
I hate myself more than anyone. I always think I have to get my act together, but I end up cowering, running away, sniveling. I want to change. I want to be a competent person.
At some point, Kaigaku also cleared Final Selectionto join the Demon Slayer Corps. Although he was expected to stand for the greater good, he remained quite selfish and never truly embraced the true spirit of being a swordsman. So when he ran into Kokushibo, his self-preservation instincts kicked in, and he agreed to join Muzan’s forces. The Demon King, like Jigoro, recognized his talent and eventually shared his blood with him before accepting him as the new Upper Rank Six, following the death of Gyutaro and Daki.
When Jigoro eventually learned about this, he was heartbroken. Feeling guilty of the far-reaching consequences of his teachings, he committed seppuku.Once Zenitsu learned about Kaigaku’s decisionand what that had done to his master, he was overcome by rage and a feeling of vengeance.
Who Has the Upper Hand?
Kaigaku Might Have an Advantage Over Zenitsu
As mentioned earlier, the Infinity Castle trilogy is going to adapt a few battles. The trailer has already revealed that Tanjiro will face Akaza,while Shinobu fights Doma. Kokushibo is also going to get involved at some point. Most fans are excited to see these Upper Moons fight at full potential, but all of their battles are going to be somewhat one-sided, despite the demon slayers teaming up with their peers.
In this regard, Kaigaku’s battle with Zenitsu stands out because the power difference is not as overwhelming between the two. They have also trained under the same mentor and understand each other’s techniques quite well. Their shared past makes them even more determined as they truly wish to win at any cost. Since Zenitsu is going to fight his old bully alone, he is unlikely tomanifest a Demon Slayer Mark. Without it, he will be extremely vulnerable.
However, Kaigaku does not really have theexperience of the other Upper Moonsand has been promoted to his position just recently. He has not had the time to adjust to his newfound powers or to innovate moves that are refined enough for a high-stakes battle. But receiving Muzan’s blood obviously means that he can now use a Blood Demon art, which is still a mystery for Zenitsu. It remains to be seen how dangerous it will be on the battlefield.
Grandfather wasn’t senile. If I’m scum, then you’re trash. I feel sorry for grandpa for having such pathetic successors. I can only do the First Form and you can do everything except that! ~ Zenitsu to Kaigaku
On the other hand, Agatsuma has also shown glimpses of greatness on a few occasions in the past. Although hecan only use one form of Thunder Breathing, he has invented new extensions for the technique that give him an edge in battle. But that will surely not be enough for an Upper Moon. Zenitsu will have to innovate a new strategy, or he might become extremely vulnerable against Kaigaku. The only advantage he has is knowing his old bully very well, but it’s uncertain if that will be of much help in an actual fight.
Zenitsu’s battle with Kaigaku might not be as one-sided as other fights teased in the trailer, but it is still heavily skewed in favor of the latter. Agatsuma will have to pull off something really special to win, or he might not survive to fight Muzan.
Demon Slayer: Infinity Castle trilogy’s first installment is scheduled to be released in the United States onSeptember 12, 2025.
