Kaigaku Personality: A Ruthless and Arrogant Opportunist

Updated: Monday, December 22, 2025

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Alignment

Neutral Evil

Kaigaku is a supporting antagonist in the anime Demon Slayer. He is a former Demon Slayer who uses the Breath of Thunder, a sword technique that mimics lightning. He is the senior disciple and rival of Zenitsu Agatsuma, the main protagonist's friend and fellow Demon Slayer.

Kaigaku's Personality

Kaigaku is a ruthless, arrogant, opportunistic, and selfish person who values strength and talent above all else. He is cruel, sadistic, and disrespectful to others, especially those he deems weak or inferior. He has no loyalty or gratitude to anyone, not even his former master or comrades. He is driven by his ambition to become the strongest and will do anything to achieve his goal, even if it means betraying his own kind and becoming a demon.

Kaigaku's personality stems from his harsh upbringing as an orphan who had to survive on the streets by stealing and gambling. He learned to rely only on himself and to never trust anyone. He developed a cynical and nihilistic view of the world, believing that only the strong can survive and that the weak are doomed to suffer and die. He also became obsessed with money and power, seeing them as the only means to escape his miserable life.

Kaigaku's life changed when he was taken in by Jigoro Kuwajima, a former Thunder Hashira (Pillar) of the Demon Slayer Corps, who taught him the Breath of Thunder. Kaigaku saw this as an opportunity to hone his skills and become a powerful swordsman. He respected Jigoro as his master, but he also envied and resented him for his status and achievements. He felt that he deserved to be the next Thunder Hashira, and that Jigoro was holding him back by favoring Zenitsu, his other disciple, who was timid and cowardly in Kaigaku's eyes.

Kaigaku's resentment towards Zenitsu grew over time, as he witnessed Zenitsu's hidden potential and talent, which surpassed his own. He constantly bullied and belittled Zenitsu, trying to make him quit or give up. He also mocked him for his feelings for Nezuko Kamado, the main protagonist's sister and a demon who retained her humanity. Kaigaku hated Nezuko for being a demon, and Zenitsu for being a traitor to his own kind.

Kaigaku's turning point came when he encountered Kokushibo, the Upper Rank One of the Twelve Kizuki, who was also a former Demon Slayer and a Breath of the Moon user. Kaigaku was easily defeated by Kokushibo, who offered him a choice: to die or to become a demon. Kaigaku chose the latter, abandoning his humanity and his allegiance to the Demon Slayer Corps. He rationalized his decision by claiming that he was following the path of the strongest, and that he had no regrets or remorse for his actions.

Kaigaku's personality did not change much after becoming a demon, except that he became more arrogant and cruel. He gained a Blood Demon Art that enhanced his Breath of Thunder, allowing him to create black lightning that inflicted fatal wounds on his enemies. He also rose to the rank of Upper Rank Six, replacing Daki and Gyutaro, who were killed by the Demon Slayers. He took pride in his new position and power, and looked down on the other demons and Demon Slayers alike. He also developed a twisted sense of humor, enjoying the suffering and despair of his victims.

Kaigaku's final confrontation was with Zenitsu, who came to avenge Jigoro, who had committed seppuku after learning of Kaigaku's betrayal. Kaigaku taunted and provoked Zenitsu, calling him a weakling and a fool. He also revealed that he had killed several of Jigoro's former students, who had come to stop him from becoming a demon. He expressed his disdain and hatred for Jigoro, Zenitsu, and Nezuko, and declared that he would kill them all. However, he was ultimately defeated and killed by Zenitsu, who used the Breath of Thunder's First Style: Thunderclap and Flash, a technique that Kaigaku could never master. Kaigaku died in shock and disbelief, unable to accept his defeat.

Relationships

Jigoro Kuwajima: Kaigaku's former master and a former Thunder Hashira. Kaigaku respected, envied, and resented him. He betrayed him by becoming a demon, and killed several of his former students. He was unaware that Jigoro had committed seppuku after learning of his betrayal.
Zenitsu Agatsuma: Kaigaku's rival and former junior disciple. Kaigaku hated him for his timid personality and hidden talent. He bullied and mocked him, and considered him a traitor for his feelings for Nezuko. He was defeated and killed by Zenitsu, who used a technique that Kaigaku could never master.
Kokushibo: Kaigaku's savior and superior. Kaigaku encountered him, and was offered a choice: to die or to become a demon. Kaigaku chose the latter, and rationalized his decision by claiming that he was following the path of the strongest. He admired and obeyed him.
Muzan Kibutsuji: Kaigaku's master and lord. Kaigaku became a demon and joined the Twelve Kizuki under his command. Kaigaku served him loyally and faithfully, and shared his goal of destroying the Demon Slayer Corps and creating a world where only the strong can survive.
Nezuko Kamado: Kaigaku's enemy and target. Kaigaku hated her for being a demon, and for being the sister of Tanjiro and the object of Zenitsu's affection. He wanted to kill her along with the other Demon Slayers. He did not recognize her humanity or her ability to resist Muzan's influence.

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