Move the decision forward. Then build.

I move ambiguous new ventures, stalled PoCs, and products that become slower with every change toward the evidence and implementation needed for the next decision.

fyber.studioA cross-store search engine for pre-owned fashionProduct design & development

More developers are not always the answer.

01

The problem is not missing requirements. It is an undefined decision.

Adding detail to a specification does not help when no one has defined what user behavior or business evidence would justify the next investment. The first deliverable should not be a feature list. It should be a testable decision and the evidence required to make it.

02

The PoC succeeds when it runs, not when it answers the business question.

A demo with clean inputs does not show whether people will use it, whether the operation is sustainable, or whether the economics work. If everything must be rebuilt afterward, both the code and much of the learning fail to carry forward.

03

The existing system holds business decisions hostage.

When impact is difficult to predict, tests are missing, and only one person understands the system, even a small change requires a large estimate. What looks like a delivery-speed problem is often an inability to judge and contain the risk of change.

Put decisions and implementation back in the same loop.

I do not simply receive requirements and build them, or offer technical advice and leave. We define what must be learned, implement the smallest reliable way to learn it, and use the result to make the next decision.

01

New ventures, PoCs, and MVPs

Before turning an idea into a specification, we identify the assumption most likely to invalidate it and the evidence needed for the next decision. I build the smallest product that can be tried in a real workflow and carry the result into the next stage of development.

  • Testable hypotheses and stop-or-invest criteria
  • A minimum implementation that reaches real users
  • Measurement, feedback, and the next decision
  • Data and architecture that can support production
02

Web products and internal systems

Before building the requested screens, I trace the actual inputs, decisions, handoffs, permissions, and exceptions. We remove unnecessary work first, then build the system around the work that remains.

  • Workflow, permission, and exception design
  • Interface, API, and data-model implementation
  • Authentication, payments, and integrations
  • Migration, operations, and failure handling
03

Improving products that have become difficult to change

Rather than implementing requests in arrival order, I determine whether growth is constrained by user drop-off, operational load, performance, or change risk. Product improvements and the engineering work needed to make the next change safer move together.

  • Bottleneck analysis from usage and code
  • Feature, interface, and journey improvements
  • Performance, reliability, and security work
  • Tests and incremental redesign
04

Technical decisions backed by implementation

I evaluate architecture, technology choices, estimates, vendor proposals, and existing code in the context of the business constraints. The result is not advice that ends in a meeting: the reasoning is documented, and I implement the critical parts when needed.

  • Architecture, technology, and estimate review
  • Roadmap and technical-risk prioritization
  • Boundaries between vendors, internal teams, and hiring
  • Design, implementation, and review of critical work

unvalley

Software Engineer

I am a Tokyo-based software engineer. Alongside building products within technology companies, I contribute to open-source software used by development teams around the world.

Frequently asked questions

Can we start before the requirements are settled?

Yes. Instead of filling in a specification prematurely, we clarify the user, the behavior that needs to change, the business assumption, and the technical uncertainty. Only the minimum scope needed for the next decision is then defined.

Can you work alongside our internal team or development partner?

Yes. I can take responsibility for stalled decisions between business and engineering, difficult architecture, implementation, or review. We define ownership at the start so the role complements the existing team rather than duplicating it.

Can an existing PoC be taken into production?

That depends on its code, data model, authentication, operations, and quality controls. I retain what is sound and replace only the assumptions that do not hold in production. A complete rewrite is not the default.

Do you also build AI features and AI-assisted products?

Yes. I work on AI-enabled workflows, production AI features, AI prototype productionization, and team adoption of coding agents in addition to conventional product development.

Move a stalled product forward.

A 30-minute online conversation about the idea, PoC, existing product, or technical decision that is preventing the work from moving forward.