The voice actor Yuki Kaji, best known for voicing Eren Yeager in the hit anime Attack on Titan, announced on his official Instagram page that he will leave Vims talent agency to pursue a voice AI project.
Kaji has voiced notable characters like Eren Yeager (left) and now the AI synthesizer Soyogi Soyogi (right), as illustrated by “Attack on Titan” author Hajime Isayama | Image courtesy of PR Times
A New Voice AI Project
Beginning April 9, Kaji will assume the role of CEO of the newly established company Soyogi Fractal. The voice AI project was built around the voice synthesis software, Soyogi Soyogi, which utilizes Kaji’s voice.
Developed after a successful crowdfunding campaign and in partnership with the voice synthesis engine Cevio AI, the software was released in December 2025 and currently supports both English and Japanese. According to the company website, the concept originated from Kaji’s desire to create a platform where both professionals and amateurs could explore creativity without constraints.
In the software’s self introduction, the character declares, “I am AI, but I have many emotions,” before demonstrating a variety of tones designed to meet various voice acting needs.
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Kaji said that as AI technology continues to evolve, raising concerns about its impact on human-made art, his decision to go independent and focus on Soyogi Fractal is driven by a hopeful vision of a future where “humans and AI resonate together.”
“I firmly believe in, and wish to protect, the irreplaceable value of the ‘soul of the human voice’ — something only a living person can create,” he said.
Kaji will complete his remaining projects with Vims by April 8, 2026.
Many voice actors gathered for a campaign against generative AI | Image courtesy of @NOMORE_MUDAN X page
Criticisms Against AI
In 2024, Kaji was among the 26 Japanese voice actors who, together with the Japanese Actors Union, called for regulations regarding the use of generative AI — specifically for audio and visual content that mimics their voice.
“Our voices are our business tool, our very lives. They are being used by AI without our permission. Please listen to how we voice actors feel,” said Ryusei Nakao in one of the campaign videos.
In the fourth campaign video, Kaji stated that passion comes from the human soul, noting that fans should respect creators and be mindful of what they support.
“It’s not that generative AI is inherently bad, but someone will be hurt when it’s used without permission,” he added.
Yuki Kaji at the 27th Tokyo International Film Festival in 2014
Kaji’s Influence in the Anime Industry
Counting his time with Vims and a previous agency under the same group, Kaji has spent a total of 22 years affiliated with the company.
“It is no exaggeration to say that this was the place that nurtured my entire career as a voice actor… they discovered me, believed in me, and helped lay the foundation for who I am today,” he wrote on Instagram.
During his tenure, Kaji has taken on numerous notable roles including Shoto Todoroki in My Hero Academia, Kenma Kozume in Haikyuu!! and Meliodas in The Seven Deadly Sins.
Kaji was also the first and — and remains the only — voice actor to win the “Best Lead Actor” award at the Seiyu Awards for two consecutive years.
