Kaigaku is one of the demons in Demon Slayer: Kimetsu No Yaiba. He is primarily featured in the Infinity Castle Arc. Among the Twelve Kizuki, Kaigaku holds the Upper Moon Six rank. He replaced Daki and Gyutaro to be in this position after they died.
Kaigaku used to be a Demon Slayer. He and Zenitsu were taken in by Jigoro, the former Thunder Hashira, and taught how to use Thunder Breath. He made up his mind to take over for Jigoro and become the new Thunder Hashira.
But sometime during the Hashira Training Arc, Kaigaku met Upper Moon Rank One, Kokushibo and lost to him. He was astonished by Kokushibo’s strength and abilities. To save himself, he gave himself up to Kokushibo and became a demon. He later joined the Twelve Kizuki.
Kaigaku is an absolute beast when it comes to power, and even though he became a demon recently, he was super powerful. The primary reason behind this is that he received a lot of Muzan Kibutsuji’s blood to turn into a demon because people who use Total Concentration Breathing are less affected by the Demon King’s blood.  Zenitsu also said that in the short time between the Hashira Training Arc and the Infinity Castle Arc, Kaigaku had eaten a lot of people, which was another sign of how strong he was.
In a year’s time, Kaigaku would have become immensely powerful and would have killed Zenitsu in an instant.
As a Thunder Breathing user who became an Upper-Rank demon, Kaigaku has excellent speed and reflexes.
This is because the Thunder Breathing swordsmanship style puts a lot of emphasis on being quick and moving in short bursts. This, along with the fact that he absorbed a lot of Muzan’s blood, makes Kaigaku a very fast fighter.
He was able to keep up with Zenitsu, a Demon Slayer who learned the same Breathing Style from the same teacher and even beat him for most of their fight.
His sword skills are different from most Demon Slayers’ because he wears his sword sheath on his back instead of on either side of his waist.
Still, he was just as good with a sword as Zenitsu, who had fought Upper-Rank demons before. Kaigaku’s swordsmanship also got a lot better after he learned the Blood Demon Art.
Kaigaku Breathing Style: Thunder Breathing
Jigoro, who used to be the former Thunder Hashira, taught this breathing style to Kaigaku. Jigoro wanted Zenitsu to be like Kaigaku when it came to learning this Breathing Style.
However, Kaigaku was unable to learn the first and most basic form of Thunder Breathing, Thunderclap, and Flash, even though he was able to learn and master the other 5 techniques of this Breathing Style.
Kaigaku’s Thunder Breathing has become real since he became a demon and learned the Blood Demon Art. He can now control natural lightning and electricity, which gives this Breathing Style a lot more offensive power. Kaigaku even said that he had gotten better than “Thunder Breathing.”
Kaigaku Blood Demon Art: Electrokinesis
In addition to his Thunder Breathing Breathing Style, Kaigaku’s Blood Demon Art gives him special electrokinetic powers that let him create and control black lightning and electricity from his own flesh and blood.
This lightning-like Blood Demon Art creates a unique effect that cracks, rips, and burns the flesh of his target, making his attacks much more dangerous and effective.
Kaigaku is very good at using this Blood Demon Art. He combines lightning with his Thunder Breathing techniques to increase the range and speed of his attacks.
Second Form: Rice Spirit
Kaigaku quickly sends out five curved slashes that are accompanied by lightning.
Third Form: Thunder Swarm
Kaigaku attacks the enemy from all sides by surrounding them with waves of arched lightning.
Fourth Form: Distant Thunder
Kaigaku makes a ball of electricity that sends waves of strong lightning bolts in many directions.
Fifth Form: Heat Lightning
Kaigaku sends lightning along with a long-range upward sword slash.
Sixth Form: Rumble and Flash
Kaigaku sends out a series of powerful lightning attacks with a long-range that hits his opponent from far away.
Kaigaku Sword: Flesh Nichrin Katan
Kaigaku carries around with him a sword made from his own flesh and blood that is a modified version of the Nichirin Sword he used when he was a Demon Slayer.
His flesh katana has a yellow blade with a black lightning pattern on both sides. The handle is black and gold.
His katana is sharper and lasts longer than a standard Nichrin Sword. It’s also possible that his flesh blade helps him use his Blood Demon Art because he can use it to channel his blood when he uses his techniques.
Zenitsu X Kaigaku
Zenitsu vs Kaigaku is a truly intense battle in the series Demon Slayer: Kimetsu No Yaiba. This is even more interesting because Kaigaku and Zenitsu both were under the same master, Jigoro, and were to become his successor.
The Mocks Before The Battle
Zenitsu meets Kaigaku behind a door as he walks through the castle. He tells him to get up and leave. Kaigaku doesn’t like how Zenitsu doesn’t respect him, so he tells him that’s not the right way to talk to a senior.
Zenitsu says that, now that he is a Demon, Kaigaku is no longer his senior. Kaigaku makes fun of Zenitsu, saying that he looks bad and is still just a weakling. He then tries to anger Zenitsu by asking if he has become a Hashira. Zenitsu responds calmly that Kaigaku seems happy to be the lowest-ranked Upper Rank, even though he’s just filling an empty spot.
Zenitsu even wanted to know why Kaigaku turned into a Demon since he used to be very interested in learning Thunder Breathing and becoming the successor to the previous Thunder Hashira and their senpai, Jigoro.
He then takes out his anger on Kaigaku by telling him that he was the one who killed Jigoro.
Kaigaku says that he thinks only people who know his worth should care about him. He then makes fun of Jigoro by calling him a “senile old man.” Zenitsu calls him back on this.
Kaigaku gets angry at what Zenitsu says about him, so he tells Zenitsu not to put him in the same boat as him. He pulls out his sword and starts the fight.
The Fight Between Two Claps of Thunder
Kaigaku tries to kill Zenitsu with his Blood Demon Art-enhanced Thunder Breathing, Fourth Form: Distant Thunder. Zenitsu, quick as he is, draws his sword and slashes past Kaigaku’s neck, calling him trash and saying he was too slow.
Kaigaku sees that Zenitsu is a much better swordsman and has a lot more skills than he did before. But he still thinks that Zenitsu, no matter how hard he trains, will never be able to beat an Upper Rank like him.
Kaigaku then uses Thunder Breathing, Second Form: Rice Spirit, to cut Zenitsu. Zenitsu says that Kaigaku has eaten too many people and asks him if he doesn’t know what is right and wrong. Kaigaku proudly says that he does know what is right and wrong.
As Kaigaku uses Thunder Breathing, Third Form: Thunder Swarm, he says that those who judge him correctly and accept him for who he is are right, and those who don’t accept him are wrong.
Kaigaku then uses Thunder Breath, Fifth Form: Heat Lightning, and teases Zenitsu while praising his own Blood Demon-enhanced Forms. He says that when his Thunder Breathing forms cut Zenitsu’s body, his skin and flesh burn and break apart as he uses the Thunder Breathing, Sixth Form: Rumble and Flash.
Zenitsu thinks about his past relationship with Kaigaku as he falls. He thinks about how he and Kaigaku did not get along. He jumps onto a wall and uses his own breathing style, Thunder Breathing, Seventh Form: Honoikazuchi no Kami. Kaigaku’s head is cut off as he falls, and Zenitsu curses him as they both fall.
Kaigaku Dies and Zenitsu Wins
Yushiro saves Zenitsu when he falls. Yushiro makes fun of Kaigaku by telling him that it is sad to die alone. Kaigaku has a horrible death, and Zenitsu is saved.
Meeting The Master
As Yushiro works on Zenitsu, he falls asleep and wakes up in a dream world where he sees Jigoro. He apologizes to Jigoro for not being able to get along with Kaigaku, and Jigoro tells him, “Zenitsu, you are my pride and joy.”
Kaigaku looks like a young man with black hair and turquoise eyes when he is a human. After he turns into a demon, he gets many demon-like features, such as fangs, pale skin, sharp black nails, and pointed ears.
Kaigaku often wears a black kimono with a blue obi over his yellow flame-like markings on the chest of his Demon Slayer uniform.
Kaigaku if not becoming a demon, could be one of the finest demon slayers and even aim to become the Thunder Hashira. But, he chose a different path and eventually paid for his life in the end.
Frequently Asked Questions
Who wins in Zenitsu X Kaigaku
Zenitsu. During the intense battle between Zenitsu and Kaigaku, Zenitsu turns out to be the winner. He was severely injured and would most likely have died if not been saved by Yushiro.
How did Kaigaku become a demon?
Sometime during the Hashira Training Arc, Kaigaku met Kokushibo, who was an Upper Moon Rank 1. He was surprised by how solid and powerful Kokushibo was. He gave himself to Kokushibo and turned into a demon in order to save himself. Later, he became one of the Twelve Kizuki.
What Rank is Kaigaku?
Upper Moon Rank Six. Kaigaku, after becoming the demon from taking in Muzan’s blood and eating a lot of humans, becomes exceptionally powerful.