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Get out of here...You gonna make me repeat myself? Leave my sight. You know why. The way you cry like a baby all day long. Aren't you ashamed of yourself? Good for nothing, any effort spent on you is an absolute waste of time. Our teacher is an extraordinary man. [..] Hey you, don't go being all familiar and calling him gramps! He's a former Hashira, someone who earned the highest title in the Demon Slayer Corps. Hardly anyone ever gets the chance to be trained by a former Hashira. The time he spends training you is all for nothing. It's infuriating to see! I hate even looking at you so get out! Why are you even here? Why do you insist on clinging on like a patch of mold?!
~ Kaigaku berates Zenitsu in the past.

Kaigaku (獪岳 Kaigaku) is a minor antagonist in the manga/anime series Demon Slayer: Kimetsu no Yaiba. As a human, he was a Demon Slayer and Zenitsu Agatsuma's fellow classmate under the former Thunder Hashira Jigoro Kuwajima. After transforming into a demon, he became a member of the Twelve Kizuki, holding the position of Upper Rank Six following the death of Daki and Gyutaro.

At some point after he joined the Demon Slayer Corps, he was defeated by Kokushibo while on a mission and quickly surrendered to save his own skin, which led him to become a demon and later rise to the Upper Ranks of the Twelve Kizuki. His betrayal would lead Kuwajima to commit seppuku out of his remorse for his pupil's crimes and the Demon Slayer Corps to brand him as his traitor.

Ironically, even though he was able to grow much stronger as a demon and to become a Upper Rank, Kaigaku would ultimately pay the price for his treachery and cowardice when he was finally slain by his archenemy Zenitsu during the Infinity Castle Arc.

He is voiced by Yoshimasa Hosoya (who also voiced Wave in Akame Ga Kill! and Reiner Braun in Attack on Titan) in Japanese and by Alejandro Saab (who also voiced Trebol in One Piece, Derrick Arden in Black Butler, Kaiju No. 9 in Kaiju No. 8 and Atsushi Kanamoto in Sword Art Online) in English.


I always side with those who properly acknowledge me, whenever and at any time.
~ Kaigaku to Zenitsu at their reunion, displaying his opportunistic tendency.
Those who correctly evaluate me and know my value are good! Those who have a low estimation of me are evil!
~ Kaigaku's twisted moral compass.

Although diligent and talented, Kaigaku was an arrogant opportunist with an inflated sense of self-preservation. Like many orphans living on the streets, he grew up resorting to thievery and other immoral means to survive. Yet unlike other orphans who joined the Demon Slayer Corps, he never developed a desire to protect people or slay demons.

Hypocritically, Kaigaku claims to follow the strong and despise weakness. He bullied and belittled Zenitsu for his lack of dignity or perseverence. Yet deep down, Kaigaku was also a coward, who cowered in fear at Kokushibo and knelt in front of him, willingly accepting Muzan Kibutsuji's blood and becoming a demon as a result, and did what Zenitsu himself would not do, sell out his mentor and fellow pupils to the demons. Additionally, unlike other demons, he retained his memories after his transformation, showing that his evil nature was as genuine as it came.

Kaigaku had also shown no remorse for his own treachery and cowardice, even insulting his master, Jigoro Kuwajima, as a worthless weakling just like Zenitsu after discovering the latter committed suicide out of shame. Furthermore, even after having been defeated by Zenitsu and on the brink of death, he felt no regret for any of his actions, only feeling excitement in the hope that Zenitsu would die alongside him. After Zenitsu was saved by Yushiro, Kaigaku screamed in rage as his body disintegrated into ash.


Early life[]

Kaigaku was an orphan and a thief, who had to eat scraps and steal to survive. This established a certain belief in his head, he started to believe that strength was the only thing worth respecting, and those who can‘t see true strength or are too weak aren’t worth respect.

First Treachery[]

When he was a child, Kaigaku was one of the orphans Gyomei Himejima cared for at his temple, and had rely on theft and eating scrap to survive. However, he had developed a self-serving view upon survival. After he was caught by the other children for stealing temple money, he was chased out at night. After that, Kaigaku encountered a Demon, which he then let into the temple in exchange for having his life spared, in order to seek revenge against Gyomei and other children. It eventually caused Gyomei to be wronged and sent into prison, until he had been rescued and joined the Demon Slayer Corps.

Second Treachery[]

After acknowledging the Demons' existence, Kaigaku decided to become a Demon Slayer in order to become strong. During his career as a Demon Slayer, Kaigaku was taken in by Jigoro Kuwajima, the Thunder Pillar, along with Zenitsu, and taught the Breath of Thunder style. Kaigaku became determined to become Jigoro Kuwajima’s successor and the new Thunder Pillar. However, Kuwajima revealed that Zenitsu would become his successor, since Zenitsu had potential to master the First Form of Thunder Breathing, while Kaigaku had never mastered it even after mastering the other Forms from the Second to the Sixth.

Believing he was losing his master's favor, Kaigaku began to despise Zenitsu for being merely a weak and timid man who earned his master's favor out of dumb luck. Thus, he started to bully Zenitsu constantly.

Later on, Kaigaku went on a solo mission to hunt down Kokushibo, the Upper Moon One, but was overpowered. After the defeat, Kaigaku kneeled before Kokushibo and begged for his life. Kokushibo offered Muzan's blood to turn Kaigaku into a demon, which Kaikagu accepted, causing his transformation into a man-eating savage. After finding out that his student betrayed him and renounced humanity, Kuwajima committed seppuku out of shame.

Infinity Castle Arc[]

I know what right and wrong is! Those who appreciate my talent is the right, those who don't and denounce me is the wrong!
~ Kaigaku reveals his values.

After the deaths of Daki and Gyutaro, Kaigaku was promoted to become Upper Moon Six of the Twelve Demon Moons due to his power and confronted Zenitsu as a rematch he always desired. Zenitsu revealed his master's demise to his teacher's classmate, accusing Kaigaku for the one to blame, but Kaigaku nonchalantly disagreed with his former classmate, believing that those who praise him were good and those who don't were evil. To make matters worse, Kaigaku didn't care about his master's death for ignoring him. Disgusted, Zenitsu called Kaigaku a piece of trash who can never master Thunder Breathing - First Form, and decided to part ways with his former prefect.

Since Kaigaku had yet to master his Demon Skills fully, Zenitsu ultimately won the duel with his newest technique, Thunder Breathing: Seventh Form: Flaming Thunder God. Kaigaku scornfully commented that their master does favor Zenitsu more for teaching him that style, until Zenitsu revealed that Flaming Thunder God was his own making, in order to fight alongside Kaigaku as equals.

Hearing this, Kaigaku watched in shock and anger as his old classmate was saved by Yushiro. Eventually, Kaigaku's head screamed in anger as he disintegrated. Yushiro scornfully declared that Kaigaku will be given nothing since he never learned how to give, and Kaigaku's die-alone fate was sealed once he decided to let his desire inflate and take him over.

Powers and Abilities[]

Blood Demon Art (血鬼術 Kekkijutsu):

  • Electricity Manipulation: Complementing his breathing and combat style, Thunder Breathing, Kaigaku can use his Blood Demon Art to generate and manipulate electricity. Kaigaku mainly infuses electricity with his swordsmanship to enhance the power of his attacks and to make up for his inability to perform its simplest technique: First Form: Thunderclap and Flash. Furthermore, his electricity has been demonically enhanced, creating a gash that cracks his opponent's flesh and burns it, greatly augmenting the lethality of his attacks. This also turns the electricity he manipulates a deep shade of black. To make matters worse, the cut made by Kaigaku's Blood Demon Art expands and spreads onto other body parts. Had Zenitsu not having the fortune to encounter Yushiro who had medical knowledge in time, the former would have died from his wounds.
  • Thunder Breathing (雷の呼吸 Kaminari no kokyū):

Kaigaku was taught by a former Hashira, Jigorō Kuwajima in the usage of this Breathing Style and immediately stuck out as a natural prodigy due to having mastered it easily. But despite his natural talent, Kaigaku was was unable to learn the first form of the Breathing Style regardless of his expertise of learning the other styles of the Thunder Breathing.

  • Second Form: Rice Spirit (弐ノ型 稲魂 Ni no kata: Inadama) - Kaigaku unleashes five electrified arching slashes all in a single moment. Interestingly, Inadama is also his surname (revealed in Kimetsu Academy)
  • Third Form: Thunder Swarm (参ノ型 聚蚊成雷 San no kata: Shūbun Seirai) - Kaigaku surrounds his target with powerful waves of electricity and sword slashes that slice up the enemy in all directions.
  • Fourth Form: Distant Thunder (肆ノ型 遠雷 Shi no kata: Enrai) - Kaigaku generates powerful lightning strikes in several directions with his blade from a far distance, effectively turning his sword into a makeshift gun.
  • Fifth Form: Heat Lightning (伍ノ型 熱界雷 Go no kata: Netsu Kairai) - Kaigaku unleashes a powerful ranged electrified sword slash upwards that burns the flesh of his target.
  • Sixth Form: Rumble and Flash (陸ノ型 電轟雷轟 Roku no kata: Dengō Raigō) - One of the most powerful Thunder Breathing techniques. Kaigaku releases a series of powerful ranged electricity attacks that strike his opponent from multiple directions.



  • Kaigaku is one of the two Upper Ranks to have ever been slain by a Demon Slayer in single combat, the other being Gyokko. He is also the only Upper Rank to have never fought against a Hashira.
  • Kaigaku's name (獪岳) contains the following symbols: Kai (獪), meaning wily or sly, and Gaku (岳), meaning big mountain. Combining those letters together, it is roughly translated as "a man who deludes himself into being bigger than he really is", hinting at his large ego.
  • As Zenitsu was only able to use the first form of Thunder Breathing, the other five forms of Thunder Breathing weren't revealed until Kaigaku used them. However, since Kaigaku had already been transformed into a demon by the time the other five forms made their debut in the story, it's likely that these forms were corrupted and didn't accurately depict how they should be performed.
  • Kaigaku and Kokushibo are the only known Demon Slayers to have become demons themselves. Coincidentally, Kokushibo was also the one who turned Kaigaku into a demon by giving the latter some of his blood.
  • Due to the movement pattern of Thunder Breathing's first form, it's likely that Kaigaku wasn't able to master it because he placed his scabbard on his back instead of on his waist.
  • Kaigaku is a dark reflection of what Zenitsu could have become if he'd allowed his fears and insecurities to consume him.
  • Kaigaku is one of the three demons who were confirmed to have turned into a demon by someone other than Muzan himself. The other two demons were Gyutaro and Daki, as they were turned into demons by Doma. Coincidentally, all three of them held the position of Upper Rank Six before their deaths.

External Links[]


            Kimetsu no Yaiba logo1 Villains

Demon King
Muzan Kibutsuji

Twelve Kizuki
Original Upper Moons
One: Kokushibo | Two: Doma | Three: Akaza | Four: Hantengu | Five: Gyokko | Six: Daki & Gyutaro

Replacement Upper Moons
Four: Nakime | Six: Kaigaku

Lower Moons
One: Enmu | Two: Rokuro | Three: Wakuraba | Four: Mukago | Five: Rui | Six: Kamanue

Former Lower Moons
One: Ubume | Two: Hairo | Six: Kyogai

Muzan's Lesser Followers
Shizu Shinazugawa | Temple Demon | Kyogai’s Mansion Demons | Snake Demon | Susamaru and Yahaba | Hand Demon | Swamp Demon | Spider Family (Father Spider | Mother Spider | Brother Spider | Sister Spider)

Tengen Uzui’s Father | Gyutaro and Daki's Mother | Kyogo Shinazugawa | Iguro Family | Doma's Parents | Kanao Tsuyuri's Parents