These are the 10 details of Demon Slayer Infinity Castle that you Missed

Demon Slayer: Kimetsu no Yaiba is an absolute hit, a franchise with the highest level of animation produced by studio Ufotable, and it truly has a global impact.

Now, the final arc of the manga is being adapted into a movie trilogy and has already broken major box office records in many parts of the world.

However, there are 10 details of Demon Slayer Infinity Castle that, even if you’ve watched the first movie of the trilogy, you most likely didn’t notice.

These are the 10 details of Demon Slayer Infinity Castle that you Missed

So, what exactly could have gone unnoticed even by the most dedicated Demon Slayer fans? Let’s start by talking about Muzan himself and what the anime hid about him.

1 – Muzan is neutralizing the medicine that should turn him into a human

Muzan can be seen for a few moments in the Infinity Castle, appearing inside a cocoon surrounded by veins. Here, Muzan is actively neutralizing the medicine created by Tamayo and Shinobu, a drug designed to turn demons back into humans. This seems to be one of the few things that has a direct effect on Muzan.

Unfortunately for Tamayo and the other Demon Slayers, Muzan remains highly confident even in this state. He absorbed the medicine at the end of season 4, but it was never mentioned again.

2 – Tanjiro and Zenitsu are at Hashira level

Tanjiro and Zenitsu went through many challenges and had significant growth. In the movie, Giyu points out that Tanjiro’s skills rival those of a Hashira. Zenitsu even defeated an Upper Moon on his own with a breathing style he created himself.

The requirements to become a Hashira include defeating 50 demons or killing a member of the Twelve Kizuki while holding the Kinoe rank. Although Tanjiro and Zenitsu defeated members of the Twelve Kizuki, they were never promoted to Kinoe.

This suggests that past Demon Slayers may have become Hashiras with far less strength compared to Tanjiro and Zenitsu. Evidence of this lies in the fact that Daki single-handedly defeated seven Hashiras.

3 – The Master originally had five children

Many viewers were confused to see the twin daughters supposedly killed mapping the Infinity Castle. But the sisters who died in the explosion that destroyed Muzan were actually the two eldest twins. Kagaya and his wife originally had four daughters and one son.

4 – Kiriya Ubuyashiki is the same child shown in season 1 of Demon Slayer

Kiriya hasn’t appeared in the anime since season 1, so it’s natural for some viewers to forget him. However, he is the same black-haired child shown during the final selection exam in the first season. Kagaya disguised Kiriya as a girl to prevent others from discovering he had a son.

Had his gender been revealed, Kiriya likely would have become a target. With Kagaya dead and the Infinity Castle being the final battle, it makes sense for Kiriya to assume Kagaya’s role.

5 – Zenitsu’s sparrow never reached the Infinity Castle

Zenitsu has a cute sparrow as his messenger instead of a crow like the other Demon Slayers. He named the sparrow Chuntaro and developed a bond with it throughout the story.

However, Chuntaro never managed to enter the Infinity Castle. Even Tanjiro’s and Inosuke’s crows got in, but Chuntaro remained outside, in the real world. This also explains why Zenitsu’s victory over Kaigaku was never announced to the other Demon Slayers.

6 – Nezuko is in the middle of her transition from demon to human

Nezuko is one of the main characters of the series and probably the most beloved by fans. However, in the final arc, Nezuko is absent, appearing only once for a few seconds while asleep.

This happens because she had already taken Tamayo’s medicine to turn her back into a human. Since Demon Slayer is in its final arc, it makes sense for Nezuko’s story to reach its conclusion. The anime never shows her taking the medicine — it’s only mentioned that she’s in hiding.

7 – Akaza’s Blood Demon Art reflects Koyuki’s hair accessories

The early part of the Infinity Castle arc focuses on Akaza. A touching detail is how his Blood Demon Art subtly mirrors Koyuki’s hair accessories.

Everything about Akaza revolved around the person he loved most. Even after forgetting his memories and becoming a demon, Akaza’s soul remained tied to Koyuki.

8 – Akaza begins to evolve into Muzan’s state

This isn’t stated directly, but as you know, the only thing that can kill Muzan is sunlight. Regarding Akaza, after Tanjiro cut off his head, Akaza reached a state similar to Muzan.

He managed to regenerate his head. Douma briefly comments on this, and Akaza even felt like a completely different being for a moment. Kokushibo also mentions that Akaza abandoned the path to greater strength. This suggests that, at that moment, Akaza was the only demon other than Muzan who couldn’t be killed.

9 – Tanjiro’s “mistake” against Akaza saved everyone’s lives

At a key moment in the fight against Akaza, Tanjiro managed to sneak behind him and could have cut his head off — but instead he shouted Akaza’s name.

Because Tanjiro defeated Akaza fairly, Akaza admitted his loss even after regenerating his head and becoming much stronger. If not for Tanjiro’s kind nature, Akaza would have killed both him and Giyu. This so-called “mistake” ended up saving everyone in the Infinity Castle.

10 – Akaza’s vest pattern references Koyuki’s name

What is the origin of Akaza’s clothing pattern? It had long been a mystery. But his backstory revealed it was far more meaningful and emotional.

The pattern on Akaza’s vest reads “Koho no Yuki,” which translates to “snow on a lonely mountain.” This means the design is a tribute to Koyuki.