Hi, I’m Masaki. Product Designer & Builder.

9+ years of experience designing and coding B2B products from accounting software to developer tools.

  • Security AI Agent Design

    [2025]
    GMO Flatt Security logoGMO Flatt Security

    Takumi is Japan’s first security AI agent capable of autonomously conducting vulnerability assessments. I led the UX and product design, navigating through a critical strategic pivot: transforming conversational agent into a high-trust agentic platform. By aligning technical constraints with user expectations, I helped evolve Takumi into a reliable partner for 60+ companies.

    • User Interview
    • Journey Mapping
    • UX Strategy
    • UI Design
    • Frontend Implementation

  • 0-1 Pulse Survey Experience

    [2024]
    freee logofreee

    For many SMEs, employee mental health is a critical business risk, yet traditional "once-a-year" stress checks often identify issues too late. I led the rapid development of a new "Pulse Survey" feature for freee, transforming a compliance-focused tool into a proactive health management platform. By acting as both PM and Designer, I utilized domain modeling to align stakeholders and engineers, enabling a high-speed release cycle without sacrificing long-term technical integrity.

    • Product Management
    • User Story
    • Journey Mapping
    • Usecase Diagram
    • Information Architecture(UI Flow)
    • UI Design
    • Frontend Implementation

  • 0-1 Product Design for Complex Workflows

    [2023]
    freee logofreee

    The launch of freee’s new product for tax accountants was a strategic move to evolve from a standalone accounting tool into a comprehensive business platform. I led the design process from discovering high-impact pain points through research to architecting a scalable information model. By balancing long-term technical value with pragmatic delivery, I ensured a high-quality release that streamlined complex tax firm operations.

    • User Research
    • Persona Creation
    • Information Architecture
    • UI Design

  • Onboarding redesign

    [2024-2025]
    GMO Flatt Security logoGMO Flatt Security

    Redesigning the onboarding flow to make vulnerability assessment setup self-serve and transparent. Eliminated engineering support dependency and reduced time-to-value.

    • User Testing
    • Prototyping
    • UI Design
    • Customer Support

  • Legacy dashboard redesign

    [2020]
    freee logofreee

    Redesigning the accounting dashboard to make cash flow management more intuitive. Significantly increased user engagement and usage.

    • Stakeholder Interview
    • User Interview
    • Prototyping
    • UI Design

I also build products as a weekend developer

See Products I BuiltMamenote recipe library displayed on an iPhone