Zenitsu Agatsuma vs Kaigaku is a battle that took place in the Infinity Castle. It focuses on the battle between Demon Slayer Zenitsu Agatsuma against Upper Rank Six Kaigaku.
Prologue[]
Zenitsu, while walking through the Infinity Castle, encounters his old senior, Kaigaku, whom he hears talking from behind a door within a large room. He tells the demon to come on out as he knows it's him. Kaigaku hears this and dislikes the lack of respect Zenitsu shows, telling him that it is not the correct way to talk to his senior.
Zenitsu responds that, because he has become a demon, he no longer considers Kaigaku as his senior and denies him for defecting to them. In response, Kaigaku sneers at Zenitsu that he is shabby and still just a weakling, trying to provoke him by asking if Zenitsu had become a Hashira within their time apart or if he could've learnt to use anything other than Thunder Breathing's First Form. Zenitsu calmly retorts that Kaigaku seems thrilled to be the lowest-ranked of the Upper Ranks, despite the fact that he is simply playing stopgap by occupying the empty positions of the previous Upper Rank Six demons.
Zenitsu shaming and reminding Kaigaku that he is only a replacement for the Upper Ranks.
Intrigued by Zenitsu's insult, Kaigaku laughs and says that he now knows how to talk back. Zenitsu wants to know why Kaigaku became a demon, since he used to be someone who was once so passionate about learning Thunder Breathing and becoming the previous Thunder Hashira's successor. He proceeds to let out his frustration on Kaigaku by claiming he was the cause of Jigoro, their master's, death, since Kaigaku becoming a demon was the reason he had chosen to commit seppuku but died a slow, agonizing death on his own without anyone to help him cut his throat or heart. Kaigaku believes that he has no reason to care or have pity for Jigoro as he declares only those who know his value are worth caring about and proceeds to reveal how he is actually relieved to learn about his demise, stating he never received the successor title despite his long efforts of trying to constantly please him. He then continues to mock Jigoro, calling him a senile old man.
This is met with great disdain from Zenitsu, who immediately overflows with anger, retaliating the insult by replying with the factor that Kaigaku had mastered all of the Thunder Breathing techniques yet never managed to learn the first which Zenitsu had overcome, also remarking at how it is pitiful for Jigoro to have never gotten a true successor. The comment makes Kaigaku enraged towards him, and demands Zenitsu not to lump him in the same boat as him. He draws his blade and begins to initiate the battle.
Battle[]
Kaigaku clashes Zenitsu with Second Form: Rice Spirit.
Kaigaku attempts to kill Zenitsu using his Blood Demon Art enhanced Thunder Breathing, Fourth Form: Distant Thunder, but Zenitsu, as quick as he is, draws his sword and easily dodges past before slashing Kaigaku's neck, calling him trash and saying he was too slow to react. Kaigaku realizes that Zenitsu is much more versatile and skilled with his swordsmanship than before. However, he still believes that no matter how much Zenitsu trains, he can never defeat an Upper Rank like him. Zenitsu then is slashed by Kaigaku with the Thunder Breathing, Second Form: Rice Spirit. Zenitsu remarks that Kaigaku has eaten too many people and questions him on whether he can tell what is right from wrong, to which Kaigaku pridefully responds that he does.
Zenitsu defeats Kaigaku using Seventh Form: Honoikazuchi no Kami.
As Kaigaku uses the Thunder Breathing, Third Form: Thunder Swarm, he says that those who judge him correctly and accept him for who he is are correct and those who don't accept him are wrong. Kaigaku then uses the Thunder Breathing, Fifth Form: Heat Lightning and taunts at Zenitsu, boasting and praising his own techniques enhanced by his Blood Demon Art. He explains that once his Thunder Breathing forms slash Zenitsu's body, his abilities crack apart and burn skin flesh as he uses the Thunder Breathing, Sixth Form: Rumble and Flash. While falling, Zenitsu reflects on his relationship with Kaigaku before in the past, and recalls how he and Kaigaku could not get along. After inwardly apologizing to the boy he had thought as a brotherly figure, he jumps onto a wall and uses Thunder Breathing, Seventh Form: Honoikazuchi no Kami, beheading Kaigaku in a single quick attack mid-air, much to the demon's absolute shock.
Aftermath[]
"Zenitsu, you are my pride and joy."
Immediately after Kaigaku is beheaded, both of Jigoro's former pupils fall down a chasm of the Infinity Castle. Kaigaku curses Zenitsu as they plummet deeper, confused by seeing a technique of Thunder Breathing that he was never taught before by his master. He then accusatorily gripes that Jigoro had favourited Zenitsu all along to which he responds by clarifying how Jigoro would never push one of them aside and that the form he used was his own special creation and originally hoped they could fight side-by-side using it. Zenitsu then passes out from exhaustion.
Kaigaku continues stewing in his disbelief, fury, and envy, but he takes a modicum of comfort in his belief that Zenitsu would fall to his death. While falling, however, he is interrupted by Yushiro flying upwards. The disguised demon scorns Kaigaku for his life-long avarice and selfishness, ending his berating by claiming that it is pathetic to die alone. Kaigaku's decapitated head finally disintegrates completely and Zenitsu is rescued and brought to safety. As Zenitsu lays there while being treated by Yushiro and surrounded by a group of Demon Slayers, he dazes off and wakes up in a dream world where he sees Jigoro, As he apologizes to Jigoro that he was unable to get along with Kaigaku, Jigoro looks up to him and says "Zenitsu, you are my pride and joy."
Due to his injuries and exhaustion from his fight with Kaigaku, Zenitsu was carried by Murata for the rest of his time in the Infinity Castle, only getting back on his feet following it's collapse and subsequent battle against Muzan Kibutsuji.
References[]