Jobs in Japan
Explore hand-picked jobs in Japan for English speakers across tech, education, marketing, and more.
Vetted companies only. Apply from overseas.
Explore hand-picked jobs in Japan for English speakers across tech, education, marketing, and more.
Vetted companies only. Apply from overseas.
RakutenAs a Senior AI Engineer you will own a business unit engagement end to end. You sit inside their engineering team and build with them: designing the agent, selecting and evaluating the model, writing the prompts and tool-use logic, and getting it live in production on our own infrastructure. You are expected to operate independently - taking a vague business ask, turning it into a concrete and evaluable LLM task, and being accountable for it shipping. What you build also becomes reusable: the cookbooks, recipes, and reference implementations the rest of the team and other business units start from. This role sits close to the product rather than close to the model: You will not be training or fine-tuning foundation models - that sits with our model research and training teams. You will not be building the LLM platform itself - that sits with our platform engineering teams. You will be embedded in a business unit, writing agent and integration code inside their product, and accountable for it shipping on our models.
- Over 6 years of professional software engineering experience, with recent hands-on focus on building LLM applications. You are shipping this work today. - Proven agentic engineering experience: you have built, shipped, evaluated, and debugged agents in production - tool and function calling, multi-step orchestration, and the failure modes that come with them. - Prompt and context engineering as a discipline: structured outputs, systematic iteration against evals, and versioning. - Practical model knowledge: the strengths and weaknesses of open-weight and commercial models, when to fine-tune versus prompt versus retrieve, and the cost and latency trade-offs of each. - Solid production fundamentals: APIs, backend services, testing, observability, and experience with self-hosted or cloud inference (e.g., vLLM). - Able to work embedded in someone else's engineering team, communicate directly with business stakeholders, and operate with the ambiguity of a function that is still being defined. - Writes things down - docs, examples, and recipes other engineers can actually use.
- Japanese language ability - a significant plus. Our business unit teams work in Japanese day to day, and being able to work in the language directly makes the embedded model far more effective. - Experience migrating production applications from third-party LLM APIs to self-hosted or open-weight models. - Retrieval-augmented generation at production scale. - Exposure to fine-tuning or post-training, enough to know when to reach for it. - Experience delivering with distributed teams in Japan or Asia.
