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Animating the Essence of Nature in Ayumu Watanabe’s ‘Children of the Sea’

The director discusses bringing Daisuke Igarashi’s 2006 manga to life in a dazzling, iridescent, and beautifully animated film that captures the complex bonds between all living things.

The cry of a newborn child, the song of a humpback whale and the birth, and death, of a star--all parallel symbols in the Japanese animated film Children of the Sea, brought to life with dazzling, dancing, iridescent animation that beautifully encapsulates one cinematic subject.

“The theme of this film is ‘The mystery and joy of life,’” says Ayumu Watanabe, the film’s director. “And that everything is a part of the universe.”

Children of the Sea (Kaijū no Kodomo), now available from GKIDS on Digital, Blu-ray and DVD, as well as on Netflix, is a 2019 adaptation by Studio 4 °C of a 2006 manga series of the same name by Daisuke Igarashi, who also wrote the film's screenplay. Not only is Children of the Sea Watanabe's first theatrically released film since his 2014 animation, Space Brothers #0, it is also the first animated reimagining of an Igarashi manga.

“I am a fan of Igarashi-sensei, and always wanted to make his work into a movie,” says Watanabe, who directed the film alongside producer Eiko Tanaka. “My dream came true when producer Tanaka approached me with this project. I wanted to let the world know of this splendid artist and author, and I wanted to animate his wonderful art.”

The story centers around a young girl named Ruka, who seeks a summer solace from her abrasive classmates and alcoholic mother at her father’s aquarium. There, she meets a spirited boy named Umi, who seems to be more at home in the aquarium tank with the fish and whale sharks than he does on land. Ruka’s father says Umi and another boy named Sora were raised in the sea by manatee-like creatures called dugongs. The boys were found by marine biologists off the coast of the Philippines and have since been kept at the aquarium for observation, with the scientists hoping to help extend Sora’s and Umi’s abnormally short lifespans.

The film poses many dense hypotheticals about the meaning of existence and the bonds between all living things. As Ruka spends more time with Umi and Sora, learning from them the secrets of the sea, the sky, and her own unique connection to the comets and creatures that inhibit both, she begins to understand the difference between greed for power through knowledge and the purity of longing to understand one’s place in the universe.

“Igarashi-sensei was hoping for new discoveries by animating his work,” Watanabe explains. “The original manga was aiming for a complete story that included the interpretation of the readers. So, we talked about if the film should take the same approach, and I was happy when he told me I could do as I pleased.”

Watanabe’s film found a balance between a convoluted and conveniently explained story, where the motifs of the film--such as the “sea sparkle” and whale mother--are named and interpreted in the dialogue while still leaving room for audience interpretation. But Watanabe and Tanaka’s endeavor to bring Children of the Sea to life to life was an ambitious one for more reasons than tackling a philosophically complex message. They also had to bring movement and unimaginably beautiful color to Igarashi’s intensely detailed illustrations, while staying as true as possible to the original manga artwork.

During film close-ups, character eyes shine like multi-colored sea glass in the sun, eyelash and eyebrow hairs can be counted and every lip crease and skin wrinkle is accounted for. The film’s animation fluidly shifts from texturized scrapbook sketches, to 2D animation, to CGI in as little as two seconds for almost every scene, with each color, sparkle and movement in the animation meant to reflect an aspect of nature.

“If I took the time and looked closely at each panel, I was able to feel the temperature and smell the aroma,” Watanabe shares. “I worked hard to put all of that into the film. Although I think I caused much trouble to the animators working on it. I am grateful that everyone gave so much of their precious time to this film.”

The hard work paid off. Children of the Sea won both the Mainichi Film Award for Best Animation Film as well as the Grand Prize Japan Media Arts Festival Award for the Animation Division, and critics have had high praise for the film’s visuals and aesthetics. Watanabe says a significant amount of their efforts in the animation were spent trying to get the “best things about both hand-drawn and CG elements.”

“I tried to make organic images while seeking warmth and ambiguity in everything that was depicted in the film,” says the director. “Instead of looking at each shot or section individually, we looked at the film as a whole to come up with ideas. I know it sounds contradictory, but I challenged myself to create CG that didn’t look like CG.”

Because of the film’s 2D-inspired CG style, scenes in Children of the Sea look multi-layered and have considerable visual depth, which highlights its realism and texture, while amplifying the imaginative, fantastical essence of the story. This is further expressed through many scenes being told from Ruka’s visual perspective, where viewers can only see the peripheral vision and depth of field Ruka does as she reaches her hands out to Umi, Sora and into the ocean with sea creatures rushing past her.

To Watanabe, that’s the whole purpose of bringing this story to life through animation.

“I was shocked when I first watched Hayao Miyazaki’s Nausicaa, and I saw the possibilities of expressing self through drawings and animation,” Watanabe reveals. “I thought that animation can overcome all restrictions to share thoughts with the world.  I believe what humans draw will reach other humans, and I wanted the viewers to feel like they were part of this film.”

He adds, “I think that humans have expressed their respect and gratitude toward nature since the ancient times. That led to imagining about the unknowns in the universe. To draw and animate is to amplify reality. I think that’s why animation was the right choice as a medium to tell Ruka’s story. Nature and the time spent around it is a theme I will always go after as a filmmaker.”

Now that Children of the Sea is available on DVD and Netflix’s streaming service, accompanied by the familiar string compositions of Princess Mononoke and Spirited Away composer Joe Hisaishi, more people than ever have the chance to journey into the deep blue with Ruka, Umi and Sora. While the film’s storyline has been criticized for its obtuse nature, Watanabe encourages viewers to indulge in their own confusion, in the film’s other message of “the more we see, the less we know,” and find a relatability to Ruka who herself says at the end of the story, “I don’t know anything.”

“Whether the audience relates to some parts of the film or disagrees with other parts of the film, I want them to cherish both feelings,” says Watanabe. “I am excited that everyone in the world will see the film and I would love the audience to let me know how they felt after watching it.”

Director Watanabe is currently at work on his next film with Studio 4 °C, Poupelle of Chimney Town.

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Victoria Davis is a full-time, freelance journalist and part-time Otaku with an affinity for all things anime. She's reported on numerous stories from activist news to entertainment. Find more about her work at