In January 2023, while still completing his Ph.D. at UC Berkeley, Akio Kodaira launched an AI VTuber named Shizuku on YouTube. She could chat with viewers in Japanese and English, sing songs, and respond in real time with a Live2D avatar. Akio ran dozens of streams, building a community of thousands of followers who tuned in to talk with an AI character that actually felt present.
At the time, this seemed like a hobby project. In retrospect, it was a proof of concept for something much bigger.
The “something much bigger” became clear if you looked at Akio’s body of research. He was the lead author on StreamDiffusion, a breakthrough paper that achieved real-time image generation at over 90 fps—fast enough for live video applications. The open-source implementation has over 10,000 stars on GitHub and was published at ICCV 2025.
That conviction is now Shizuku AI.
The company is building an AI lab in Japan dedicated to developing AI companions and characters—combining cutting-edge research with the artistic sensibility that has made Japanese character design beloved worldwide. The initial focus is on Shizuku herself: expanding her capabilities with multilingual voice synthesis, richer conversational AI, and presence across platforms like Discord, YouTube, and X.
Akio is tackling a fundamental challenge facing AI companions today: they lack the data to generate truly engaging, proactive conversations, which makes interactions feel monotonous. By deploying Shizuku across multiple platforms and building a community that participates in her evolution, the team is creating the feedback loop needed to solve this problem.
The community-driven approach is intentional. Akio believes that characters worth loving can’t be built in isolation—they need to grow through relationships with real people, just as the most iconic characters in Japanese entertainment have always evolved through the bond between creators and fans.
Akio brings expertise from his time at Meta, where he worked on real-time video generation, followed by a research role at Luma AI. He has the rare combination of world-class technical ability, deep cultural intuition about what makes characters resonate, and years of hands-on experience actually building and operating an AI character that people want to spend time with. Most founders have one of these. Akio has all three.
Growing up in Japan, Akio was shaped by stories of humans coexisting with artificial life: Doraemon, Mega Man Battle Network, and countless anime where AI companions weren’t just tools but partners and friends. He watched Hatsune Miku become a global phenomenon, proving that Japanese characters could transcend language and culture. And he became convinced that AI would eventually make these fictional relationships real.
We’re thrilled to lead Shizuku AI’s seed round. In the coming age of AI agents, we believe theirs will be the ones people genuinely want in their lives. Akio has been working toward this future longer than almost anyone, and we couldn’t be more excited to help him realize it.
If you’re passionate about AI companions, character design, or the intersection of technology and entertainment, Shizuku AI is hiring in Japan and beyond.
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Justine Moore is a partner on the investing team at Andreessen Horowitz, where she focuses on AI — both foundation models and applications.
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Marco Mascorro is a partner at Andreessen Horowitz, where he invests in AI infrastructure companies.
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Martin Casado is a general partner at Andreessen Horowitz, where he leads the firm’s infrastructure practice.
