by Demon Slayer: Kimetsu no Yaiba The Movie: Mugen Castle Arc Chapter 1: Akaza Returns is currently showing in theaters, captivating audiences with its breathtaking visuals and emotional intensity. To coincide with the film’s release, a new behind-the-scenes making-of video has been unveiled, offering rare insight into ufotable’s famously “overwhelmingly inefficient” yet uncompromising animation process—a philosophy that continues to set the studio apart in the global animation industry.
What Is “Demon Slayer: Kimetsu no Yaiba”? (Beginner Overview)
Demon Slayer: Kimetsu no Yaiba is based on the manga by Koyoharu Gotouge, published by Shueisha’s Jump Comics. The complete series spans 23 volumes and has achieved an extraordinary global circulation of over 220 million copies, making it one of the most successful manga franchises of all time.
The story follows Tanjiro Kamado, a kind-hearted boy whose family is slaughtered by demons. After discovering that his sister Nezuko has been transformed into a demon, Tanjiro joins the Demon Slayer Corps in hopes of curing her and defeating the demon king Muzan Kibutsuji. The series is known for blending tragic human drama, intense sword battles, supernatural horror, and moments of warmth and humor.
The anime adaptation by ufotable began in April 2019 with Tanjiro Kamado: Unwavering Resolve Arc and quickly became a cultural phenomenon.
The Mugen Castle Arc: The Final Battle Begins
The Mugen Castle Arc depicts the climactic confrontation between the Demon Slayer Corps and Muzan’s forces inside the demons’ stronghold, the Infinity Castle (Mugenjo)—a surreal space where gravity, perspective, and logic collapse.
This arc is being adapted as a theatrical trilogy, with Chapter 1: Akaza Returns scheduled for release on July 18, 2025. The film has already drawn global attention and was notably nominated for Best Animated Feature Film at the 83rd Golden Globe Awards, marking a rare achievement for a Japanese animated filmeven though it ultimately did not win.
A Rare Look Inside ufotable’s “Overwhelmingly Inefficient” Workflow
The newly released making-of video, titled
“Demon Slayer: Kimetsu no Yaiba Infinity Castle | Scene at The Academy,”
was published on the official Oscars YouTube channel and narrated by Takahiro Sakurai, the voice of Giyu Tomioka.
The documentary focuses on ufotable’s unique production philosophy described by the studio itself as “overwhelmingly inefficient.” Rather than relying heavily on automation or fully CG pipelines, ufotable insists on hand-drawing an enormous number of cuts, even in an era when many global studios are shifting toward full 3D animation.
Key Production Highlights
- Over 2,200 animation cuts were created for Akaza Returns
- More than five times the usual number of in-house animators were involved
- Every key drawing was individually reviewed by senior staff
This approach prioritizes artistic personality over efficiency, allowing each animator’s style to shine.
Why ufotable Still Believes in Hand-Drawn Animation
According to Hikaru Kondo, ufotable’s CEO and general director, hand-drawn animation possesses a unique charm precisely because of its “instability.” Slight imperfections, line variations, and subtle human touch create emotional depth that purely mechanical visuals often lack.
In the making-of video, Kondo explains that the studio deliberately chooses this difficult path because
“Someone’s line ignites someone else’s line.”
This chain reaction of creativity becomes the driving force behind ufotable’s signature visual intensity
Organizing Chaos: How the Film Came Together
To manage such a massive project, Kondo first established a clear framework defining:
- When each sequence would be created
- Where the visual emphasis should lie
- Who was best suited for each scene
- What emotional impact was required
The animation director Haruo Tonosaki and chief animation director Akira Matsushima personally checked all key frames, ensuring consistency while preserving individuality. Many scenes, as the staff admits, are moments that “only that animator could have drawn.”
The Impossible Space of Infinity Castle
One of the greatest challenges was visualizing Infinity Castle, a setting that defies physics, gravity, and perspective. According to finishing director Yuichi Terao, early rendering estimates suggested it would take nearly 10 years to fully calculate the visuals using conventional methods.
To overcome this, ufotable combined:
- Hand-drawn character animation
- Advanced 3D camerawork
- Digitally composited backgrounds
The result is a space that feels realistic yet unreal, perfectly matching the psychological intensity of the final battle.
As one staff member put it:
“No matter how much we draw, it never ends.”
Music as the Emotional Core
Another key element highlighted in the documentary is the role of music, which Kondo describes as “the heart of the work.” The animation, lighting, and camera movement were all carefully synchronized with the score to amplify emotional impact, especially during confrontations involving Akaza, Tanjiro, and the Hashira.
A ‘Battlefield’ Behind the Screen
The making-of video repeatedly frames production itself as a kind of battlefield. While the staff avoids calling it “hell,” the comparison to the relentless struggle against Muzan Kibutsuji feels fitting. Every department animation, CG, photography, sound, and music pushed beyond conventional limits.
In the end, this grueling process produced visuals that are not just technically impressive, but emotionally resonant.
Why This Making-of Matters
This behind-the-scenes feature is more than just promotional content. It demonstrates why Demon Slayer: Kimetsu no Yaiba continues to stand out worldwide:
- A refusal to compromise on artistic quality
- Respect for traditional animation techniques
- Deep collaboration between creators
- A belief that emotion begins with a single line
As the Mugen Castle Arc unfolds across its planned trilogy, ufotable’s “inefficient” philosophy proves once again that true craftsmanship leaves a lasting impact on screens, and in the hearts of audiences.
With Chapter 1: Akaza Returns now in theaters, fans can witness the results of this extraordinary creative battle firsthand
