Only Studio 4°C Would Spend 7 Years On A Passion Project Rom-Com About A Man Marrying A Fish

Studio 4°C has been on a hot streak in 2026. After GKids’ theatrical release of the time-warping dystopian romance All You Need Is Kill, the animation studio has another film release in the hopper with ChaO, a rom-com that’s more on the hilarious side of heartbreaking. In the lead-up to its release, I spoke with director Yasuhiro Aoki about how his vibrant love story took a short-film concept and turned it into a fully fledged feature film. 

Set in a fantastical future where humans and mermaids’ coexistence is as strained as oil and water, ChaO follows Stephan, a skittish inventor working at a shipping company. He has a bold plan to save the ocean from the very pollution his scandal-ridden employer is creating, which is making the mermaid king irate. No one takes Stephan’s idea seriously until his chance encounter with Chao, the mermaid princess, who proposes to him out of the blue after saving his life. What follows is a royal wedding complete with corporate spin and media frenzy, placing the newlyweds under a microscope as their marriage of convenience gradually turns into something real. 

While ChaO is opening in theaters three months after GKids’s last feature film, the movie has been in development for seven years. Moreover, the film, which marks the veteran animator’s solo directorial feature debut, is a personal project for Aoki. You see, long before Studio 4°C approached him to lead a new film project in its early stages of development, the initial concept for ChaO originated in Kung-fu Love, ten years earlier. And as fate would have it, Aoki’s 15-minute short film, which was part of Studio 4°C’s compilation music video Amazing nuts!, fit perfectly in line with what both he and Studio 4°C had in mind for a fun-loving, nonsensical rom-com.

Although Studio 4°C might not be an anime production house that new-fangled anime fans easily recall by name, the multi-award-winning studio has a reputation among old-school anime fans who were blown away by watching it and Studio Madhouse's certified classic original video anime anthology, Memories, and The Matrix’s own anime anthology series, The Animatrix. In the years since, the studio has become a quiet yet influential presence in the anime industry, delivering awe-inspiring works, including its other maritime-themed film, Children of the Sea, in 2019, and Berserk: The Golden Age Arc - Memorial Edition in 2023.

But by far, what stands out as a defining trait of Studio 4°C (besides its expressive, kaleidoscopic, and sometimes avant-garde art direction and its clever blending of 2D and 3D CG animation) is its willingness to take big risks with its projects. 

Aoki is far from a baby-faced director, having started in the industry as a co-director for 2008’s Batman: Gotham Knight and storyboard artist for Psycho-Pass: The Movie. For Aoki, the veteran animator’s journey from working in the industry to directing ChaO with Studio 4°C was a dream come true for a fanboy who grew up admiring their works when he was younger. 

 “They’re very different from other studios. They make projects that other studios cannot make—they’re free,” Aoki said. 

Of course, Aoki emphasized that even within the unique sense of freedom Studio 4°C provides to its creators compared to other studios he’s worked with, all rules remain in place. After all, all the creative freedom in the world still needs to lead to a good movie worthy of the studio’s reputation which it wears quite literally in its name. 4°C is the temperature at which water is most dense, and this is reflected in its slogan to create works that are “dense with substance and quality.” 

Likewise, when Aoki was making ChaO—a film that really turns the true love transformation trope on its head by making its charming bride a giant goldfish who becomes a gorgeous woman only when she is truly in love—he believed it was a bold, imaginative idea only Studio 4°C could pull off. But for Aoki, that feeling resonated even more deeply, as if it were the only movie he could make to mark a highlight of his career.  

“In a sense, it’s really like two opposite ends of one coin. ChaO feels like it's the culmination of all my work, but then it’s also something very different from what I was thinking I was going to make,” he said. 

Mind you, this is the same veteran animator whose distinguished career has helped create animated classics, including but not limited to Neon Genesis Evangelion, several Sailor Moon projects, Trigun, and the anime director of the classic OVA You’re Under Arrest (yes, that You’re Under Arrest). If any veteran animator has less to prove, it’s Aoki. Still, Studio 4°C’s whimsical, heartfelt rom-com about a guy falling in love with a fish girl holds a special place in the 58-year-old’s heart. 

“It’s a little hard to explain, but I really think all of it is really special to me,” Aoki said. 

A quick glance at the landing page of Studio 4°C's very rad website makes it obvious: Aoki’s love of slick mechs, dense, neon-drinched cityscapes, with a madcap romance serving as its beating heart, matches the studio’s titular wavelength. Having watched the film myself, I immediately found myself falling into the exact emotional pocket Aoki and Studio 4°C were aiming for in its near ten-year development—that rush of encountering something both so wildly new while also feeling as familiar as an animated work that left an unmistakable impression upon you as a child. Granted, my personal “member berries” watching ChaO skewed more toward early-aughts animated touchstones like Ponyo, with a dash of Corpse Bride, were worlds away from the ‘70s anime Aoki grew up on and wove into the DNA of ChaO as Easter egg references old heads will no doubt notice. 

Aoki hopes ChaO sparks that dichotomy where novelty meets nostalgia, allowing moviegoers to interpret what it all means in their own hearts. But for Aoki, ChaO is a balancing act that's contrasted with a lot of gags, big feelings, and even a little political bite, distilling his career into a romance that's as strange, tender, and luminous as Stephan and Chao themselves—something only Studio 4°C would dare to craft for the big screen after a seven-year labor of love.  

ChaO releases in theaters on April 10th.