Animated Film ‘ChaO’ Tells Love Story Between Mermaid Princess and the Guy Next Door

By Eri IshitsukaYomiuri / Shimbun Staff Writer

11:30 JST, September 5, 2025

The new animated film “ChaO” tells a miraculous story of romance inspired by Hans Christian Andersen’s fairy tale “The Little Mermaid.” It is the latest work created by Studio 4°C, which has produced many hit animated movies.

The film depicts a future society in which mermaids coexist with humans, who take their presence for granted. Stephan (voiced by Oji Suzuka), who works at a shipbuilding company, is an ordinary young man, yet he is passionate about developing screw propellers that will not harm marine life.

One day, he is suddenly proposed to by Chao (voiced by Anna Yamada), a princess in the kingdom of the mermaids. Their wedding is hyped up by the public, as it promotes friendship between humans and mermaids in a society in which marine accidents involving fish caught in screw propellers are a social problem. Carried away by the circumstances, Stefan agrees to marry Chao.

At first, Stephan cannot accept the fact that Chao looks like a fish when she is on land. However, little by little he becomes taken in by her as he sees how pure she is in her struggle to adapt to the human world that she is unfamiliar with.

Suzuka and Yamada recently sat with The Yomiuri Shimbun for an interview, and they discussed the charms of the film.

The Yomiuri Shimbun: How did you feel when you first watched the completed film?

Suzuka: The world shown in the film and the characters’ interactions are really fun. It made me laugh, moved me, and made me feel various emotions. It also has a very important theme about different species respecting each other and living together.

Yamada: The story unfolds in a place based on Shanghai, with a little bit of a magical essence added. The characters are all very colorful and unique, including the way they look, and a miraculous love story develops between them. All those factors add up to create a very nice work, I think.

Yomiuri: What were you thinking about when you voice-acted your characters?

Suzuka: Stephan is a bit of doofus, but he is a young man who eagerly faces up to his job. He makes progress during the course of the story, so I tried to show that he’s gradually becoming stronger inside when I played the part.

Yamada: Chao has a big crush on Stephan. She’s a straightforward girl who asks for his hand in marriage right after meeting him, and she also works hard to get used to doing things that are unfamiliar to her, just for Stephan. I was told to make her sound very cute, so I consciously spoke in a higher tone than usual.

Yomiuri: Both of you usually appear in live-action productions and have been successful in them. How did you find using only your voice for acting?

Suzuka: It’s always tough to speak a line within the given seconds. But the atmosphere was very friendly in the studio, so I was able to have fun even though it was a difficult task. There were times when our lines were changed on the spot because the movement of the images and the word count didn’t match, and I thought, “I am having an incredible experience now.”

Yamada: I was surprised that nothing except the lines were written in the script book. But then, because of that, we had the liberty to improvise a little in the studio. It was a tough but interesting part of the work.

Colorful and ‘photogenic’ town

Yomiuri: In June, “ChaO” won the jury award in the Annecy International Animation Film Festival in Annecy, France. I heard that the film also generated much laughter from the foreign audience. What are your favorite scenes?

Yamada: The scene in which they surprise a person playing a ghost in a haunted house at an amusement park where they go for their first date. Recording that scene was really fun, too.

Suzuka: I was thinking about the same scene.

Yamada: Sorry! (laughs)

Suzuka: There’re other scenes, too. Right after they start living together, Stephan comes home and hears Chao singing in the bathroom, so he goes to peek. That scene makes you chuckle, and I also like that he was drawn by Chao’s beautiful voice. I think it’s a richly woven scene with various emotional swings.

Yomiuri: The world shown in the film is attractive, too. Drawn in bright colors with attention to detail, the cityscape is distinctly beautiful and full of energy. What would you like to do if you could go to the world of “ChaO”?

Suzuka: I like taking photos, so I’d love to take pictures of the city in that world because it’s in conspicuously vivid colors. I imagine that if you take pictures of the same place in the morning, midday, late in the afternoon and at night, they would all look different.

Yamada: A certain machine appears midway in the film, and I want to ride it … !

Suzuka: It seems like it would be fun if we could control it.

Yomiuri: [To readers] Please check what kind of machine it is while watching in a movie theater! The film’s main plot is a romantic love story, but there are various other themes, too.

Yamada: I think this is a film that makes people naturally want to consider how they can live together in a world where there are various kinds of life and races. It’s not that this theme is pushed to the foreground, but I think it’s nice that [the film] contains this very important subject.

Suzuka: Even casual lines contain deep messages. For example, there’s a scene in which Chao gives away her precious treasures to neighbors, saying she is happy having only what she needs.

Yamada: That’s a very nice line.

Suzuka: Even such important life lessons are casually sprinkled throughout this film.

Anna Yamada

Born on Jan. 8, 2001, she is from Saitama Prefecture. She made her debut in 2011 after winning a grand prix in a model audition run in a girls’ manga magazine. She played the Ainu girl Asirpa in the “Golden Kamuy” series, a live-action adaptation of the popular manga of the same title.

Oji Suzuka

Born on Jan. 11, 2000, he hails from Okayama Prefecture. He was scouted when he appeared in a film as an extra, which led to his debut. He won many awards for his performance in “Mitsubachi to Enrai” (“Listen to the Universe”) in 2019, in which he played a starring role for the first time.