I build software without surveillance baked in.
I’m Hidekazu Yamaoka, a solo developer in Fukuoka, Japan. iOS, Next.js, and Cloudflare-native systems for founders who don’t want to ship trackers along with their products.
🇯🇵 Fukuoka, Japan · Async-only · Email-first · Monthly retainers from $2,500
No project managers, no committees. Your request hits the keyboard the same day.
What I build
A focused stack, used in production for years. No frameworks-of-the-month, no experimental features in your codebase.
iOS / SwiftUI
Native apps with Apple Watch, Live Activities, and StoreKit 2. 4 apps shipped to the App Store.
Next.js / TypeScript
App Router, Tailwind, Vercel. The same stack that runs ai-autosite.com (77+ tools, monthly visitors).
Cloudflare / Supabase
Workers for low-latency APIs, Supabase for auth and Postgres, RevenueCat for subscriptions.
Why a Japan-based studio
Three things that aren’t obvious until you start working with someone 16 time zones away.
Your nights are my workdays
When something breaks at 11 PM in San Francisco, I’m already 16 hours ahead — on my morning coffee, ready to ship a fix before your team starts their day.
Quiet reliability, by default
Software culture here treats precision and durability as defaults, not features. Tests get written. Edge cases get handled. Documentation exists before it’s needed.
Favorable economics
A strong dollar against the yen means you get senior-level work at honest USD rates without sacrificing quality, attention, or commitment.
One person, no overhead
The same thing that makes agencies expensive is what makes them slow: layers of people between you and the work. A studio of one removes the layers.
Decisions in hours, not days
No kickoff meetings, no estimation rounds, no internal approvals. You email me on Monday morning, I’m writing code by Monday afternoon.
One person, end to end
The person reading your inquiry, writing the code, and sending the invoice is the same person. No handoffs, no account managers, no "let me check with the team."
Pivots without paperwork
Change your mind about a feature mid-sprint? Just tell me. There’s no change-order process, no scope-creep meeting — I update the plan and keep moving.
How I work
Four principles, applied consistently. They’re what make a one-person studio possible.
Async-only
Email, Loom, Linear. No standups, no calls. Senior-level work delivered in deep-focus blocks.
Privacy by default
No analytics SDKs, no fingerprinting, no IDFA. Your users’ data stays where it belongs.
Your code, your IP
Full IP transfer on delivery. Your data and code never enter any AI training pipeline.
Honest about tools
I use modern AI-assisted tooling. I take full responsibility for every line that ships.
Monthly retainers
Month-to-month. 30-day notice to cancel. No long-term lock-in.
You’re not buying time — you’re reserving capacity in a studio of one.
Care
Maintenance & small improvements
- Bug fixes & dependency updates
- Small feature additions
- Monthly 30-min written review
- Email support
Ideal for: Existing apps that need a steady hand
Email meBuild
Active product growth
- Async delivery on small tasks within 48h
- One mid-size feature sprint per month
- Bi-weekly Loom progress updates
- Architecture Decision Records (ADRs)
Ideal for: Seed–Series A SaaS in growth mode
Email meBuild Pro
Privacy-critical or parallel work
- GDPR / CCPA design reviews included
- Dedicated Linear workspace
- Overnight Japan-time coverage
- Detailed ADRs on every change
Ideal for: Privacy-sensitive SaaS, healthtech MVPs
Email meFounding Engineer
Embedded engineer slot
- Up to one other client maximum
- Weekly written sync
- Roadmap & technical strategy input
- Full IP assignment to your company
Ideal for: Early-stage startups without a CTO
Email meNot sure yet? Pilot Sprint — $3,500 for 2 weeks of focused work on one scoped problem.
The boring parts, done properly
Most software relationships break down on the unglamorous stuff: invoices, status updates, deadline communication, handoffs. These are written into the contract, not handled on a best-effort basis.
Replies within one business day
Every email gets a real human reply, not an auto-responder. If the answer needs research, you get an acknowledgment first and the answer next.
Deadlines are commitments, not estimates
If a deadline is at risk, you’ll know at least 48 hours in advance — with a written explanation and a revised plan, not a last-minute apology.
Itemized invoices, monthly, on the 1st
Every invoice lists hours, deliverables, and a brief change log. USD totals are locked at the previous month’s exchange rate. No surprise charges, ever.
Every change documented in writing
Architecture Decision Records on every meaningful change. Loom walkthroughs on every release. Your future self (or future hire) will thank you.
Clean handoffs, even if you cancel
Cancellation includes a written handoff document, credentials transfer, and 30 days of email-only support — included in the contract, not a paid extra.
Quiet hours respected — yours and mine
I don’t fire Slack messages into your team’s evening. P1 incidents are the only exception, and they get a phone-tree escalation, not a midnight ping.
Selected work
Products I’ve designed, built, and shipped under my own studio. They’re what your retainer would look like in practice.
Tuck Voice
Voice memos that think for themselves
Record, transcribe on-device with Whisper, and search every word — privately. Native iOS, no servers involved for transcription.
DealKit
Deal management for creators
CRM-style brand deal tracker for influencers. Shipped on iOS and Android in 9 days from design to App Store release.
TimeSee
Visual timer for ADHD brains
See your time. Drag once, feel it through haptics. Native iOS with Apple Watch companion and Live Activities.
ai-autosite.com
77+ free tools, zero tracking
A growing library of privacy-first web tools running on Next.js, Tailwind, and Cloudflare. Open source under MIT.
A note on AI in my workflow
I work with modern AI-assisted tooling. In 2026, that’s the same as saying I use a code editor with autocomplete — it’s how professional software gets built today.
What matters more is what I commit to:
- I take full responsibility for every line that ships, including correctness, security, and IP.
- Your code, configurations, and business data never enter any third-party AI training pipeline.
- Every meaningful decision is documented in an Architecture Decision Record so you can audit anything later.
Honesty about tools is part of the privacy-first deal.
Doing the boring parts properly is the rest of it.
FAQ
Why no calls?+
How does the time difference work?+
How do you use AI in your workflow?+
Can I cancel a retainer?+
What if I’m not sure I need a full retainer?+
How do payments work?+
Are there any hidden fees or setup costs?+
Do you handle sensitive or regulated data?+
Email me about your project
The fastest way to start. Tell me what you’re building, your timeline, and your budget range. I’ll reply within one business day (Japan time).
[email protected]All inquiries are read personally. No CRM, no auto-responder, no marketing list.