The archive · AI & Models · Product decision · 2023–2026
Shizuku AI bets live AI VTubers, not chatbots, build the world's most loved AI companion
Founder Akio Kodaira turns his AI VTuber 'Shizuku' into a company; a16z leads its seed round, the first it has led for a Japanese startup.
Shizuku AI
What the business is
Shizuku AI (San Francisco-based, Japan-born) builds AI companions and characters, starting with 'Shizuku', an AI VTuber who chats live with viewers in Japanese and English, sings, and reacts with a Live2D avatar across YouTube, Discord and X.
Starting capital：Seed round led by a16z, announced February 10, 2026; amount not disclosed in primary sources
How it started
In January 2023, while finishing his PhD at UC Berkeley, Akio Kodaira launched the AI VTuber 'Shizuku' on YouTube. She could chat with viewers in Japanese and English, sing, and respond in real time with a Live2D avatar. Kodaira ran dozens of streams and built a community of thousands of followers — proof, in his telling, that an AI character could feel present. His research base included StreamDiffusion, the real-time image-generation paper he led (90+ fps, 10,000+ open-source GitHub stars, published at ICCV 2025), an internship at Meta working on real-time video generation, and a research role at Luma AI.
What happened
After roughly two years during which Shizuku was dormant, Kodaira relaunched her as 'Shizuku V2.0' and announced the formation of Shizuku AI in February 2026, with a seed round led by a16z — the first time the U.S. fund has led a round for a Japanese startup. The company is based in San Francisco but is building an AI lab in Japan, combining Bay Area research with Japanese character-design sensibility. Initial focus is expanding Shizuku's multilingual voice synthesis, richer conversational AI, and presence across YouTube, Discord and X, with a community that participates in her evolution.
How it ended up
Still early stage: as of February 2026, Shizuku AI had closed its a16z-led seed round, relaunched Shizuku V2.0, and was hiring in Japan and beyond to build an AI-companion lab.
Background
Shizuku AI is the company behind 'Shizuku', an AI VTuber launched on YouTube in January 2023 by Akio Kodaira while he was completing his PhD at UC Berkeley. She chats with viewers in Japanese and English, sings, and reacts in real time with a Live2D avatar. Kodaira ran dozens of streams and built a community of thousands of followers — early proof that an AI character could feel present rather than scripted.
Kodaira brought unusual credentials to the bet: he was lead author of StreamDiffusion, a real-time image-generation system running at over 90 fps whose open-source implementation has 10,000+ GitHub stars and was published at ICCV 2025; he interned at Meta on real-time video generation and then worked in research at Luma AI. In February 2026 he relaunched Shizuku as 'Shizuku V2.0' and announced Shizuku AI, with a seed round led by a16z — the first round the U.S. fund has led for a Japanese startup, per ITmedia and GIGAZINE.
The company is based in San Francisco but is building an AI lab in Japan, deliberately combining Bay Area research with Japanese character-design culture. The initial plan is to expand Shizuku's multilingual voice synthesis and conversational AI across YouTube, Discord and X. a16z framed the bet as solving the core AI-companion problem — a lack of data for engaging, proactive conversation — by running Shizuku live across platforms and building a community that participates in her evolution, creating the feedback loop flat chatbots cannot get.
What has to be true
- Kodaira started with a live public character instead of a chatbot, so every stream generated real conversational data rather than waiting for it.
- He combined research credibility (StreamDiffusion, 10k+ GitHub stars) with hands-on streaming experience — the pairing a16z explicitly cited.
- The bet leaned on Japanese character culture traveling globally, from anime to Hatsune Miku, to make an AI companion lovable rather than merely useful.
- a16z's first led round for a Japanese startup gave the idea institutional validation and a proof point for the AI-companion category.
What can be applied
If AI companions feel flat because they lack real conversational data, don't wait for data — make the product a live public character so every stream is both content and training signal.
Aftermath
As of February 10, 2026, Shizuku AI had closed its seed round with a16z as lead investor and officially started operations: Shizuku returned from a roughly two-year hiatus as 'Shizuku V2.0' with a relaunch stream, and the company was expanding her multilingual voice synthesis and conversational abilities while bringing her to YouTube, Discord and X. It was building an AI lab in Japan and hiring in Japan and beyond, with the stated goal of creating the world's most loved AI companion.
Sources
- Investing in Shizuku AI
- 日本発のAI VTuber「しずく」開発元、米VC大手a16zから資金調達
- 日本発のAI Vtuberをつくる「Shizuku AI」がa16zをリード投資家として日本のスタートアップとしては初となる資金調達に成功
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