Demon Slayer: Infinity Castle continues an unfortunate trend for the anime series, and lets down one of its most important characters

When it comes to Demon Slayer, there's one character who might be even more important than the titular hero this show is named after. Emphasis on "Demon," rather than "Slayer". Yet in Demon Slayer: Infinity Castle, said demon is basically nowhere in sight.

Yep, Tanjiro Kamado might be our beloved hero, but it's Nezuko, his sister, who inspires everything that the slayer does throughout this saga. She plays a vital role in this story, which is exactly why her absence at the start of Demon Slayer's final trilogy is so surprising and tough to bear (unless you've already read the manga, of course. In that case, Nezuko's removal is more disappointing than anything else).

As you might recall, only Tanjiro and Nezuko survived when a demon brutally slaughtered the entire Kamado family back at the very start of the series. But Nezuko didn't emerge unscathed. During the attack, she was transformed into a demon herself, although she did retain a small measure of humanity. To save Nezuko, Tanjiro trained to become a demon slayer in hope of protecting her and even finding a way to restore her former self. As such, the entirety of this story revolves around the bond between these two siblings, and, for a time there, it looked like that this might become even more important in the final stretch.

An unfortunate trend

At the end of the third season's Swordsmith Village arc, Tanjiro faced an impossible decision when he was forced to choose between saving Nezuko or a group of innocent people who were under attack from a demon. There wasn't enough time to save everyone, so our fave slayer was paralyzed by indecision, unable to save everyone.

More in touch with her humanity than ever, Nezuko ended up making that decision for him by sacrificing herself so that Tanjiro could save the others. But she didn't die. By fully embracing her human side, Nezuko miraculously survived the sunrise, which would have usually killed a demon like her. In doing so, Nezuko even began to recover her voice, which she had long since lost following her demonic transformation.

But then the Hashira Training arc came and went with barely any hint of Nezuko at all. Becoming more human had drained Nezuko of her energy and, without the taste of human flesh to rejuvenate her, she was essentially confined to her bed. The only scene where Tanjiro's sister made any impact was more about Zenitsu and Inosuke fighting for her affection than Nezuko herself.

That's also true of Infinity Castle. The action takes place almost entirely in said castle, aside from numerous flashbacks, and pretty much none of it features Nezuko. In fact, there's only one brief scene that shows her at all, which is basically thrown in to remind us that she still exists, tucked away from the world while everyone else fights on her behalf.

Now, there is a good reason for this, canonically speaking. The Demon King Muzan Kibutsuji has learned of Nezuko's unique ability to survive direct sunlight and he wishes to harness this power for himself. In doing so, he would become unstoppable. Muzan is already the most powerful demon to walk this earth and, if he finds a way to overcome his only weakness, then humanity is doomed.

As such, it's incredibly important to keep Nezuko away from Muzan at all costs. Losing her would lose the entire fight between good and evil. But why hide Nezuko away from us, the audience?

Even if she's not there in the midst of the fight, Nezuko deserves to be showcased far more. She's the emotional tether to Tanjiro's entire journey, the very reason why he fights in the first place, and she's also key now to the final showdown against Muzan. But, instead, Koyoharu Gotouge's manga and the anime that followed forgo this vital bond in the final stretch – and it continues an unfortunate trend for the show.

Wasted opportunities

Throughout the first three seasons, Nezuko was kept muzzled to protect those around her. And to protect Nezuko herself, she was often hidden away from sunlight in a box that Tanjiro would carry around on his back. That all makes sense, story-wise, but, as a viewer, what this means is that the show's most important female character was essentially silenced and locked up without any agency of her own. Plus, it didn't help that the animators occasionally objectified Nezuko's demonic adult form to an uncomfortable degree.

This could have all changed after season 3, though, centring Nezuko with her own voice at last. Instead, Demon Slayer went the opposite way and basically wrote her out of the story completely.

It's said that "the battles will start to center around her," so why can't Nezuko be allowed to show up in a few herself? I know, I know. She has to be kept away from Muzan. But what's stopping a few demons from seeking her out and chasing Nezuko down outside of the Infinity Castle? Yes, there's a lot going on here with so many characters to juggle, but if anyone deserves a bigger spotlight in this final stretch, it's her.

Showcasing Nezuko more in these films would reinforce that emotional bond, which gives Tanjiro the drive to win while also upping the tension as Muzan gets closer to taking Nezuko's power for himself. If we have time for a 20-minute flashback in the middle of the film's climactic battle, we definitely have time for the beating heart of this story to throw down at least once with another demon.

With two Infinity Castle films to go, there is a chance that Nezuko's role in the original story could be increased with some tweaks to the source material. So far, Ufotable has been pretty faithful to the manga, though, so it's unlikely they'd consider such a huge change this late in the game.

And that's a shame, because in a world where the fight against good and evil is paramount, it would have been fascinating to explore how Nezuko's returning humanity could blur these lines at such a critical juncture. Instead, Demon Slayer would rather ignore one of its most important characters entirely. Muzan might be the one trying to steal Nezuko's power to walk in the sun, but it's the writers who are stopping her from shining like she should.

Demon Slayer: Infinity Castle is out now in US and UK theaters. For more, check out our guide to watching Demon Slayer in order, or look ahead to the best new anime still to come in 2025.