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As io9 has painstakingly detailed, 2025 was a definitive year for animated filmsthanks in part to dazzling success at the box office of Demon Slayer: Infinity Castle. As the film gears up for awards season, its makers have shared some behind-the-scenes insight into how studio Ufotable pushed beyond its limits (and the laws of physics) to bring the megapopular anime’s explosive fights to life.
Talk with Weekly Entertainment, Infinite Castle director Haruo Sotozakidirector of photography Yuichi Teraoand president of UFOTABLE Hikaru Kondo recalled how the studio’s commitment to creating the best anime possible helped bring the film to the table this awards season.
In the film, hero Tanjiro Kamado and the rest of the Demon Slayer Corps dive straight into enemy territory, fighting off an onslaught of powerful enemies and overpowered bosses in the ever-changing maze that is Infinity Castle. Although it is not Demon Slayerthe first rodeo in the cinema, Infinite Castle marks the beginning of the end of the Banner series as the first in a film trilogy. Releasing the first leg of this trilogy in IMAX theaters inspired Ufotable to elevate the streamer anime into a cinematic experience. The studio wanted to ensure that every corner of the screen was packed with detail, which required collaboration in its composition of 2D characters moving in 3D environments in its fluid action sequences.
“If you look at a lot of the key frames, the key animation, the sakuga in this film, we worked closely with our 3D department to make sure everyone was in perfect harmony because we didn’t want any weird effects where maybe these 2D characters are sliding across the environment and 3D environments,” Sotozaki told EW. “So it was very important that the 2D keyframe animators talked to our 3D team to make sure the compositions were perfect.”
On that front, Sotozaki told EW that the most complicated aspect of setting up Infinite Castle to life was about making sure his 3D environments and animations were all in sync. To avoid errors during production, he said Ufotable often tests keyframes in their respective 3D environments before completing key animations. While the secret to hero Tanjiro’s success lies in his impeccable breathing techniques, Terao explained that Ufotable’s animators excite themselves with music so that once the pencil hits the paper, Infinite CastleThe numerous settings and sequencing momentum would flow directly into its animation.
“Whenever you see Tanjiro say, ‘Don’t give up,’ the hosts are probably doing something similar with their headphones,” Terao said. “I’m on the digital 3D side, but I know this is especially true for the keyframe animation team, the 2D animators. Whenever they want the characters to do certain actions, they sometimes get up from their desk and play out some of those action sequences. So if you see that out of the corner of your eye, you might sometimes wonder, ‘Are they just cheering or dancing or are they trying to play something to see what the animation would look like?’ It’s quite an interesting sight to see.
The biggest obstacle for the team by far was Infinite CastleThe final fight between Tanjiro and Akaza, which Sotozaki says was fought by four people in Ufotable. Chief among them was the key facilitator Masayuki Kunihirowho, according to Sotozaki, handled 80 percent of the physical breakdown fight between Akaza and Tomioka.
“It’s quite tricky action, but very fast action. I say that in a good way, but it’s unrealistic in the sense of how fast the characters can move and what they look like on screen. It’s very convincing to the viewer, but it defies physics,” Terao said. “If you’ve seen the movie, you’ll understand what we’re talking about. The first time, we’re trying different types of animation where parts of the Infinite Castle whether it breaks, shatters or collapses, there is a lot of destruction. And take, for example, when Akaza crushes the ground. It breaks and you have this smoke, but all of that has to be simulated in CG in these different physics engines.
“The irony is that when you watch Kunihiro’s animation, you flip over a paper image and the characters move about 100 meters, which is impossible in real physics. So a lot of the simulation we tried to do about how things break, doing this hybrid between 2D animation and 3D simulation was quite difficult,” Sotozaki said, getting more into the nitty-gritty of how the animated sausage was made.
He continued: “It was fun, but challenging because there’s really no setting that allows such fast physics to happen depending on how the physics engines calculate the different simulations. So I think it also has a very unique pipeline. Often we’ll have 2D action animators who match the action to the 3D environments or shot composition, but Kunihiro is the exception to that and we allow him to create the keyframes of the action first and the 3D team actually has to match the 3D environments to whatever it’s giving.”
The trio unfortunately stated that they could not provide an update on when fans can expect the second installment of Demon Slayerthe finale of the cinematic trilogy or what is the future of Demon Slayer what might look like once the trilogy is finished. This response, in concert with the Crunchyroll president’s FOMO, fueled “Better watch it in the cinema while you can” The response to anime fans asking when they can expect the movie to hit the streamer is quite discouraging.
However, Sotozaki assured fans that Ufotable would continue to strive to provide a consistent level of animation quality for the latter stages of Demon SlayerThe finale of the theatrical series.
“At the studio, we always try to meet and exceed audience expectations and create an experience that everyone can enjoy. The entire team and staff share this feeling, so do what you want with this information,” Sotozaki said.
In io9’s opinion of Infinite Castlewe also praised the film for its flashy animation and action sequencing, writing: “Ufotable’s animation is as dazzling as ever, with fluid camera movement that ping-pongs its characters across 3D CG backgrounds, complemented by a compositional finesse that gives the film a cinematic grandeur beyond that of past films like Train Mugen. Its action choreography is a roller coaster for the eyes: fluid, explosive and sometimes slowed down, as if to let sparks fly from the katana blades like fireworks behind your eyes. And his final battle kicks things into third gear.
Clearly, Ufotable’s reputation as an animation studio to watch has paid off this year, because Infinite Castle earned a Golden Globe nomination for Best Animated Feature Film. Chainsaw Man – The Movie: Reze Arc, although it is just as excellentwas not retained, so everything Demon Slayer has to do is beat his fellow nominees (including the big hitters Demon Hunters KPop And Zootopia 2.) As Issa Rae at the Emmyswe support everyone, anime.
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