WE ARE HIRING · 採用情報
Full-Stack Engineer
Tokyo
Kotoba builds frontier speech AI. We're hiring a Full-Stack Engineer to work on our SaaS products — Kotoba app, our meeting bot, and our web dashboard. Front-end-leaning full-stack, with real care for how things look and feel.
ABOUT KOTOBA
At the frontier of voice generation AI
Kotoba is a generative AI company on a mission to “become the defacto for voice AI in East Asia,” developing state-of-the-art voice generation AI models. At our core is a low-latency, high-accuracy speech translation model that connects conversations so naturally it feels as though both speakers share the same language. It supports major language pairs — including Japanese, English, Korean, Chinese, and Spanish — breaking down the language barrier. We also develop our own ultra-low-latency speech-to-text and text-to-speech models that run everywhere from the data center to edge devices, and we license this foundational technology, which powers the next generation of voice agents, to Fortune 50 companies and major U.S. tech firms. We create world-class voice AI from our two hubs in Tokyo and San Francisco.
Kotoba brings this technology to the world through its own product, the Kotoba app, available on iOS and Android. Since launch it has won explosive support across countries and regions including Japan and Korea, growing to a steady 2,000–3,000 new downloads per day. In the App Store and Google Play category rankings, it has reached No. 1 in its category, ahead of the likes of Google Translate and Audible. Loved by individual users, it is also seeing accelerating adoption among major enterprises — centered on Japan — and has supported nearly 100 events on the ground, including SusHi Tech Tokyo. It has drawn media attention as well, featured on numerous programs such as TV Asahi, NHK, TV Tokyo, Abema Prime, and PIVOT.
Kotoba was founded in 2023 by two Japanese generative AI researchers who earned their PhDs at top U.S. universities. To date it has raised a cumulative total of more than ¥3 billion (roughly US$23 million) from prominent VCs in Japan and the U.S. (including Kindred Ventures and Globis Capital Partners) and from the corporate venture arms of leading U.S. and Japanese enterprises, and it also receives strong government support in Japan for AI model training. World-class research paired with a product that keeps winning in the market — with both, Kotoba is one of the most exciting generative AI startups today.
Media
— TV Tokyo：https://www.youtube.com/watch?v=17CG6kSv2zs
— TV Asahi：https://tver.jp/episodes/epy340m62i
— PIVOT：https://www.youtube.com/watch?v=N30YYfIqGEg
Kotoba was founded in 2023 by two Japanese generative AI researchers who earned their PhDs at top U.S. universities. To date it has raised a cumulative total of more than ¥3 billion (roughly US$23 million) from prominent VCs in Japan and the U.S. (including Kindred Ventures and Globis Capital Partners) and from the corporate venture arms of leading U.S. and Japanese enterprises, and it also receives strong government support in Japan for AI model training. World-class research paired with a product that keeps winning in the market — with both, Kotoba is one of the most exciting generative AI startups today.
ROLE DESCRIPTION
THE ROLE
As a Full-Stack Engineer, you'll build the SaaS product suite centered on Kotoba app — the mobile app, our meeting bot, and the web dashboard that ties them together. This is a front-end-leaning full-stack role: your primary focus will be front-end development with a high bar for UI/UX, while going deeper into the backend whenever the work calls for it. This is not a role where you implement requirements handed to you. You'll talk with stakeholders across the company to shape those requirements yourself, bring your own proposals for what should be improved and how, and operate independently — taking real ownership of everything around our web applications. Design is a collaboration with an external design firm, and you'll work with their designers as an equal partner in refining the product's UI/UX. Our infrastructure is owned by a dedicated infrastructure engineer who codifies and operates it in Terraform. You won't need to design infrastructure yourself, but we do expect you to understand the overall architecture well enough to coordinate closely with them. Kotoba app is built specifically for enterprise customers, so you'll be building with the particular demands of large organizations in mind.
RESPONSIBILITIES
What you'll do
•Front-end development for our SaaS product suite — Kotoba app, our meeting bot, and the web dashboard — with a high bar for UI/UX.
•Full-stack feature development, going into the backend whenever the work calls for it.
•Shaping requirements through conversations with stakeholders across the company, and proposing improvements to the product.
•Collaborating with our external design firm — discussing and aligning on design, then translating it into implementation.
•Contributing to our development process and code quality, including code review.
•Coordinating with our infrastructure engineer, grounded in a working understanding of the Terraform-managed architecture.
QUALIFICATIONS
Who we're looking for
Required
•Professional experience building web applications — front-end as your core strength, with the ability to work into the backend.
•A strong point of view on UI/UX, and the ability to refine the product as an equal partner in discussions with designers.
•The ability to work independently and take ownership — from gathering input from internal stakeholders through to shaping requirements and proposing improvements.
•No infrastructure specialization required, but enough understanding of a Terraform-managed architecture to coordinate with our infrastructure engineer.
•Business-level communication skills in Japanese or English.
•A fit for the pace and intensity of an AI startup.
Preferred
•Experience building and shipping a product of your own, including side projects and personal work.
•Experience at a startup working on deals or product development for large enterprises — a feel for enterprise requirements.
•Experience working at both large companies and startups.
•Business-level Japanese
HOW TO APPLY
If you’re interested, please apply Kotoba’s hiring team directly
at hiring@kotoba.tech with your resume attached.
