Highlights
- Kaigaku is a member of Muzan’s Twelve Kizuki, with ties to Gyomei Himejima and Zenitsu Agatsuma’s past.
- Kaigaku’s betrayal led to Gyomei’s imprisonment and Jigoro Kuwajima’s death, fueling Zenitsu’s rivalry.
- Kaigaku became Upper Rank Six of the Twelve Kizuki, setting the stage for a potential confrontation with Zenitsu in the Infinity Castle arc.
Kaigaku is an important character in Demon Slayer, and you probably didn’t even notice him. It will later transpire that he is a member of Muzan Kibusuji’s Twelve Kizuki, however, did you know that you have seen him before in the anime?
He has a significant role in Gyomei Himejima’s past and was pivotal to the fates of Zenitsu Agatsuma and his master Jigoro Kuwajima. So who is Kaigaku, and where have you seen him before? It is argued that he is one of the most hated characters in the anime, here’s why.
Anime Debut |
Season 1, Episode 17 “You Must Master a Single Thing” |
Manga Debut |
Chapter 34, “Robust Blade” |
Height |
167 cm |
Kaigaku and Gyomei Himejima – Betraying a Mentor and a Family
In season four, we learnt about the roots of Gyomei Himejima, the Stone Hashira and strongest of all the Hashira. He revealed to Tanjiro that he was a mentor in a temple who looked after orphaned children. One of these children was Kaigaku, and he was not part of the majority who respected temple property or Gyomei.
The other children caught him stealing money from the temple and he was subsequently grounded from it. He was told not to return until nightfall, however Kaigaku did not come back. He ran into a bloodthirsty demon, as a result of this naughty behaviour. Out of fear and cowardice, he pointed the hungry demon to the temple, promising that it would be able to devour all inside. He also assisted the demon by snuffing out the wisteria incense that Gyomei burned every night to keep demons at bay.
As a result, seven out of eight children were killed. Gyomei tried to save Sayo, the remaining child, by punching the demon’s head in till the sun rose. Unfortunately, Sayo could not articulate to authorities that a demon caused all the bloodshed. She wailed “that man is a monster”, but because the demon disintegrated in the morning light the only man amongst the corpses was Gyomei. It appeared at face value that Gyomei murdered the children, and he was jailed as a result, set for execution. Luckily for him, a young Master Ubuyashiki saved him from the death sentence.
Kaigaku, Zenitsu Agatsuma and Jigoro Kuwajima
With no place to go, Kaigaku wound up in the care of Jigoro Kuwajima, a former Hashira and Master of Thunder Breath. Jigoro was a positive role model for Kaigaku, for he set out to become a Thunder Breath master just like his mentor. Kaigaku worked hard as a student, even becoming a prized pupil. He became so caught up in his determination that he could not handle Jigoro’s announcement of two successors instead of one, the other successor being a whiney, cowardly young boy named Zenitsu Agatsuma.
Kaigaku’s Intense Rivalry with Zenitsu
Jigoro had also adopted Zenitsu into his care, rescuing him from deep debt and raising him as a swordsman. Despite the rigorous training regimen and harsh teaching methods, Zenitsu grew a love for Jigoro, even going as far as to call him “grandpa”. This love also went both ways, for Jigoro grew to love Zenitsu, too. Zenitsu understood that Jigoro saw his potential even when Zenitsu did not see it in himself. Through all his crying and suffering through training, Jigoro did not give up on him and wanted him to never give up on himself.
Zenitsu and Kaigaku have a brief moment of interaction in a flashback scene during season one of Demon Slayer. Kaigaku was angry at Zenitsu, for he felt that he was wasting Jigoro’s time by constantly crying and wanting to give up on training. He also had a problem with Zenitsu calling him “grandpa”, for it was too familiar of a relationship. Kaigaku obviously has a deep dislike for Zenitsu, which did not bode well in Jigoro’s decision to no longer have one successor.
As his star student, Kaigaku had an impression that he would be the sole successor to Jigoro, however he decided that both Kaigaku and Zenitsu would succeed him. Kaigaku became enraged, he did not want to be aligned with someone as cowardly as Zenitsu.
Jigoro Dies From Heartbreak
Kaigaku later committed an unthinkable sin, which would in turn be the cause of his master’s death. One day Kaigaku was in a fight with Kokushibo, Upper Rank One of the Twelve Kizuki. He was clearly losing this battle to such a powerful demon, so he surrendered to Kokushibo. On top of this, he voluntarily wished to become a demon. His request was granted and he drank Muzan’s blood. He quickly rose up in demonic circles and became a member of the Twelve Kizuki. Sadly, word of this reached Jigoro and Zenitsu.
Horrified at the fate of his top student, Jigoro could not handle the pain of this news. How can someone he trained to stop these monsters become one? Unable to bear the shame and disgrace of Kaigaku’s decision, Jigoro committed seppuku. Normally another samurai is there to behead them to ensure a quick death after the belly has been sliced open. However, Jigoro wished to die alone. He did not want an audience to his decision, nor someone to explain the reason as to why he was killing himself. Yes, the blade was in Jigoro’s hand; but in the end it was Kaigaku that killed him.
At the tail end of season four, Zenitsu opened a letter that we still do not know the contents of. Manga readers know that it detailed Kaigaku’s transformation into a demon and his master’s death as a result. In the last episode where the entire demon slayer corps fell into the Infinity Castle, we see Zenitsu “locked in” as he normally is before a battle. However, brand-new to us, he is wide awake. This is chilling considering that he is usually in a sleep state when he’s locked in. That letter changed him, and we will soon see it when the Infinity Castle arc of Demon Slayer airs.
Where is Kaigaku Now?
Kaigaku has consumed enough human flesh to find his place among the Twelve Kizuki. He replaced Gyutaro and Daki as Upper Rank Six. It was just announced that the Infinity Castle arc of Demon Slayer will be split into three movies in the upcoming years. As a result, many tough battles with Muzan’s Twelve Kizuki versus the demon slayer corps can be expected. It is only fitting that we see a grueling fight with Kaigaku and Zenitsu, and perhaps uniquely what the combination of swordsman training and blood demon art can do.
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