True love never fades, holds no limits, and has no boundaries. Studio 4°C brings to you yet another stellar-performing anime film. A fairytale dream comes true when two childhood friends reconnect to get married in order to stop a war between their two nations. Oh, did we say nations? We meant species. The human race is in hot water with the mermen kingdom, and the only way to soothe the tension is with a royal wedding between an ordinary man and a fish princess. It’s a real fish out of water type situation when this impromptu couple tries to make it work for the sake of peace, only to end up falling in love all over again.
This Story is Off the Hook!
Stefan, your average salary man in the year 20XX, finds himself held down by his empathetic respect for the sea. A ship design engineer for a large multinational corporation just wanted to fulfill his dream of making ships safer in the open ocean, and to cope with the loss of his parents, which stemmed from his losing them to the sea. Every safety feature he designs is met with hostility by his boss, who wants nothing but to make his ships profitable. Tension between the humans and the Mermen continues to escalate. Neptunus, the king of the Mermen, reluctantly agrees to settle the dispute with the union of his daughter to a human. However, he left the choosing of a groom to the princess, a match no one understands but her.
A Fishy Feature
ChaO has an interesting take on mixing two love story genres of both an isekai and a “we’ve met before” type of romance comedy. Princess Chao (voiced by Yamada Anna) struggles heavily in her fish form to adapt to the life of a human, while Stefan (voiced by Suzuka Oji) adapts to his newfound popularity being married to a mermaid. Now with his spontaneous importance, Stefan gave him the opportunity to push his new ship engine propeller. The couple immediately catches waves from King Neptunus, believing that the marriage is a sham, merely a front orchestrated by both Stefan to further his career, and the company he works for to continue making a profit over protecting the ocean.
When the Line Snaps
The story takes a turn when Chao surprises Stefan with a robot mech suit, built by his long-time friend Juno, as a birthday gift during the launch of his new ship propeller. The scene erupts into chaos, forcing Stefan to save his wife before crashing the mech into the newly constructed ship. It was after that moment that Stefan had had enough. A career ruined, the company’s future in jeopardy, and still has no clue as to why Chao chose him to be her husband, he snaps at her and chases her away. Sad and alone, he thinks back to his childhood and how he lost his parents, feeling sorry for not being able to fulfill his promise to them. He goes back to his family’s fishing, thinking back to a time when they were together.
There, he remembers finding a bright blue pearl that turned out to be a fish egg. From that moment, Stefan vowed to protect that egg, even after losing his parents to a freak accident.
Mending the A Forgotten Net
Living as an orphan, Stefan got into a fight with some bullies who stole his pearl. Enraged, he swore to protect his pearl at all costs, which kind of sounded like a marriage proposal to a fish living in an egg. He lost the fight, and the pearl fell into the sea, making Stefan swim after it in vain, only being able to save the shell, and that’s when he finally remembered. Her eggshell became sort of a crushed pearl that he kept as a child that reminded him now of how they first met.
He finally remembers who she was and what he had promised her all those years ago. He knew then that it wasn’t a career or pleasing their nations that was going to make them happy. It was that they’d be happy together, and that nothing else mattered. He sailed out into the ocean in search of Chao, only to end up confronting the wrath of her father Neptunus. Once again, announcing his pledge to protect her no matter what, which caused her to reappear and make amends.
Breathing Life into ChaO
Hiroshi Takiguchi has been in the anime industry for many decades, starting off as an animator in films such as Spriggan (1998), to lead animator in Mind Game (2004), and making his way to art director of Tekkonkinkreet (2006). Hiroshi working with Studio 4°C’s animation team for ChaO has been nothing more than an absolute spectacle, albeit with their traditionally non-mainstream, unorthodox animation art style.
A seamlessly fluid animation coupled with the jagged, penciled-in, semi-finished landscape design art style blends in perfectly, much like with their previous works, such as All You Need Is Kill (2026), where rigidly complex character designs flow so effortlessly on screen.
A Whale of a Tale
Since ChaO’s debut in Japan on August 15, 2025, the film has been screened in 16 different countries around the world. It opened in the U.S. on April 10, 2026, with an estimated $27,538 and a total of $70,254 by April 12. Yauhiro Aoki had directed other films such as Steamboy (2004) and The Lord of the Rings: The War of the Rohirrim (2024). Writer Hanasaki Kino’s other works include Kuro no Sumika -Chronus- (2014) and Children of the Sea (2019). As of now, there is no date set or platform for its streaming release.
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