Demon Slayer changed the game for anime movies based on TV shows when studio ufotable decided to adapt the Mugen Train storyline into a feature film rather than a season of TV. Not only did that movie go on to become a monumental hit, but it remains a high point of anime, a self-contained story with a good balance of action and character development.
Now it seems the promise made by that movie — that Demon Slayer was not restrained by its medium and could deliver the best adaptation in the best medium for it — has fallen completely flat. That's because Demon Slayer: Kimetsu no Yaiba Infinity Castle is a major step down from what Mugen Train achieved, a movie that feels like an unedited compilation film, a poorly stitched-together series of episodes with horrendous pacing and a never-ending series of flashbacks in what is obviously a very incomplete story. Not all is lost, however, because we do get some cool character moments, some nice visuals, and arguably the best back story the franchise has done.
The movie starts right where Season 4 ended, with the Demon Slayer Corps now scattered and surrounded by hordes of demons inside Muzan's ever-shifting demonic castle dominion after an attempt to kill the king of demons failed. It goes without saying that this movie is not for newcomers, and the plot is virtually incomprehensible if you have never seen the previous seasons — much like Infinity War is not meant to be your first MCU movie. Be warned, however, that Infinity Castle is not just a continuation of Season 4 (Hashira Training Arc), but it also connects to storylines going as far back as Mugen Train. This is the start of the grand finale, after all, so we're beginning to see payoffs to several storylines.
Indeed, Infinity Castle (the first part of a trilogy) raises the stakes and makes it clear from the get-go that even if Tanjiro is probably going to make it out of this fine, the same can't be said of his fellow warriors. Whether it's in the big fights against high-ranking demons or even just in the many small skirmishes against dozens of small demons, the Demon Slayer Corps members are overwhelmed and in grave danger, which adds to the tension of the film.
The story is essentially divided into three fights. First off, we have Shinobu encountering the Upper Rank Two demon, followed by Zenitsu fighting his own personal demons, and finally Tanjiro getting his rematch against Akaza. The first two parts reach a satisfying climax to the respective character arcs, while Tanjiro also clears a big stepping stone in his story. The biggest compliment one can give this movie is that Zenitsu is finally no longer annoying, but rather gets a compelling dramatic story in Infinity Castle. The standout part of the film, however, is the back story to arguably the biggest non-Muzan villain in the franchise — Akaza. Though Demon Slayer has presented plenty of demon flashbacks in the past, this is by far the most effective one in what it says about the allure of demons, and the cruelty of humanity, all without actually excusing or condoning the actions of Akaza.
Visually, studio ufotable gets great mileage out of the Infinity Castle location, with the ever-shifting scenery adding to the danger and the stakes as characters constantly get blocked by a randomly appearing building, or transported elsewhere by a disappearing hallway. It's a creative way of breaking up the repetitive fight scenes — of which there are many. Elsewhere, the fight animation is about what you'd expect from Demon Slayer, not particularly better with the higher budget, which is more of a testament to the animators and VFX artists at ufotable than anything else in that they already deliver big-screen spectacle on a weekly basis.
That being said, a lot of the emotional pay-offs are undercut by the film's overuse of flashbacks. This is a pattern that the anime has been guilty of for a few years now, but when presented in a single feature film the flaws are more glaring. The 155-minute runtime introduces a good dozen flashbacks that intercut the fight scenes at critical moments and severely slow down the pacing while also making the runtime feel longer. This is not necessarily a dealbreaker when watching a series on TV, because you at least have a week to digest the flashbacks and the information they deliver. In a feature film, however, they get no time to breathe. It is jarring to see the huge tonal shifts the movie goes through on a scene-by-scene basis when you cut from a fight to a flashback every few minutes. Perhaps this problem will be fixed when we get the inevitable TV edit of Infinity Castle, but as it stands this is simply lacking.
