This article contains spoilers from the Demon Slayer manga and Infinity Castle Movie.

The first chapter of the Demon Slayer: Infinity Castle trilogy is finally out in Japan, while the rest of the world waits for the perfect time to see the final battle unfold on the big screen. It’s already breaking records in ticket sales, and fans know it will only continue to flourish upon international release. The only way for the Demon Slayer: Infinity Castle movie is up, meaning there’s no stopping its success.

The full title of the first movie translates to Demon Slayer: Infinity Castle—Part 1: Akaza Returns, giving a massive hint at the parts or chapters it will cover from the manga. The most obvious clue is Akaza’s name, which means the first movie of the Infinity Castle trilogy will most definitely introduce a new upper moon demon who’s more pathetic than terrifying.

picture: tanjiro kamado in a poster of infinity castle movie 1.

Demon Slayer: Will The Movies Be Fully Faithful to the Manga?

The first movie in the Demon Slayer: Infinity Castle trilogy will be released in a few months. But how accurate will they be compared to the manga?

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By Laura Gassert

Demon Slayer: Infinity Castle Part 1 Will Introduce Upper Moon Kaigaku

Kaigaku Is the New Upper Moon Six

Kaigaku replaced Daki and Gyutaro as Upper Moon Six.
The new Upper Moon Six, Kaigaku, has a shared history with Zenitsu.

Usually, when an upper moon dies, a new powerful demon takes their place to keep the order within the ranks. So, when demon siblings Daki and Gyutaro died in the Entertainment District story arc, a new demon took their place and became the new Upper Moon Six. This demon was revealed to be Kaigaku, a demon slayer turned demon after Upper Moon One Kokushibo gave him Muzan Kibutsuji’s blood before the events of the Infinity Castle arc.

And in the first movie of the Demon Slayer: Infinity Castle trilogy, Kaigaku is all set to debut his thunder breathing techniques reinforced with his demon blood, in front of his junior, Zenitsu Agatsuma. For context, Kaigaku and Zenitsu trained under the former Thunder Hashira, Jigoro Kuwajima, years ago. While Zenitsu can only use the first form of thunder breathing, Kaigaku can use all forms except the first one.

Now, Kaigaku and Zenitsu are destined to face each other in the Infinity Castle not as allies fighting on the same side, but as enemies with contradicting beliefs. Based on the trailer for the Infinity Castle movie, fans will certainly see their intense fight unfold on the big screen. Fans know there can only be one true thunder breathing successor, and the victor will automatically own the title.

Demon Slayer: Infinity Castle Part 1 Will Humiliate Kaigaku Like Never Before

Kaigaku's Pathetic Fate in the Demon Slayer Manga

demon slayer zenitsu letter infinity castle jigoro kaigaku

Kaigaku believes it’s alright to be shameful just to continue living.
Kaigaku brags louder than his thunder claps in Infinity Castle.

Even before Kaigaku became a demon, he had already lived a pathetic human life. He was an orphan who made ends meet by stealing, eating scraps, and slurping puddle water until Gyomei Himejima took him in. Instead of returning Gyomei’s act of kindness, Kaigaku lured a demon into Gyomei’s temple to continue living. This demon killed the other orphans, while Kaigaku survived.

Soon after, Jigoro Kuwajima took Kaigaku in and trained him with Zenitsu in thunder breathing. However, Kaigaku thought highly of himself, disgusted at the thought of sharing the successorship with someone like Zenitsu, who has no pride or guts. Worse, other demon slayers gossip behind Kaigaku’s back, claiming he would never become the Thunder Hashira because he failed to master its most basic form, no matter how hard he trained himself.

Until you die, you haven't lost.—Kaigaku

Kaigaku's pathetic human life did not end there, as the demon slayer Kaigaku once again begged for his life in front of an overwhelming opponent such as Kokushibo. Instead of doing his best to kill Kokushibo, he consumed every drop of Muzan's blood just to stay alive. After all, he had this fantasy that he would reap the fruits of his shame one day as long as he was alive.

Unfortunately, the Infinity Castle is no place for someone like Kaigaku to brag about his new abilities and preach his beliefs. Sure, he had grown a lot stronger than before after consuming humans, but he had no idea how to use his new techniques and abilities properly. If only the fighting had happened a year later, he would have been an unstoppable demon capable of thunder breathing.

Zenitsu’s Blade Sealed Kaigaku's Pathetic Fate

There Can Only Be One True Thunder Breathing Successor

When Demon Slayer fans saw Zenitsu open his eyes in the Infinity Castle, they knew he meant serious business. Zenitsu knew he had to deal with Kaigaku to settle their problem once and for all after reading the contents of the letter back in the Hashira Training arc. He had to set aside his fear and anxiety, knowing he wouldn’t be able to avoid the conflict with Kaigaku anymore. He knew he wouldn’t be able to face his master in the afterlife if he cowered in front of him.

I don't care about anyone who doesn't value me! At every moment, I always serve those who know my value—Kaigaku

For the first time, Zenitsu opened his eyes in the Infinity Castle arc. It’s now or never, as the perfect stage for his fight with Kaigaku has already been set. There can only be one true Thunder Breathing successor, and Zenitsu would never allow a demon like Kaigaku to own the title and damage his master’s reputation any longer.

Manga fans know that while Kaigaku’s slashing attacks can crack Zenitsu’s skin and burn his flesh, the courageous demon slayer will answer with the newest form of Thunder Breathing. In that decisive moment, Kaigaku’s head will be decapitated, and his wish to see Zenitsu die will vanish with him. Just like that, Kaigaku will die alone, unfulfilled, and bitter to the very end.

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