Tsumagoi Work&Camp
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One person built the system behind this place

Who built this, and working with us

Booking and payments, the AI chat, the kiosk at the door, the cameras and sensors: Sennin Kenji (Kenji Sakuramoto) built the system that runs this place at 1,444 m, and runs it every day. We can build the same for yours.

Talk to us about a project

All of it on one line

From the moment a guest opens the site to the moment they open the front door, these parts sit on one line.

  1. The booking site

    The site you are reading. Guests check what is free in Japanese or English, then book and pay on the spot by card, Square or PayPay.

    Built with React 19 · TypeScript · Vite · Supabase · Stripe · Square · PayPay

  2. One AI, four doors

    The site chat, LINE, the tablet by the door and the door voice: the same AI answers from the same data as the price list, and hands what it cannot answer to Sennin Kenji.

    Built with Claude · LINE Messaging API · Supabase Edge Functions · Langfuse

  3. The kiosk at the door

    An Android tablet at the door does the front desk’s job. The app updates itself over the air.

    Built with PWA · Android · OTA

  4. The site monitor

    Seven cameras, temperature and water-level sensors, power plugs and the network on one plan of the site. AI tells people from cars, and the recordings can be replayed.

    Built with Frigate · OpenVINO · SwitchBot · Ecowitt · Omada

    Read how the site monitor was built (kensaur.us)
    The site monitor: a plan of the site with the seven camera feeds and each room’s temperature on it
    The site monitor, as it runs

  5. The console

    Bookings, the shop, Wi-Fi codes and the ad numbers on one screen. Staff alerts arrive on Discord.

    Built with Supabase · Discord · GA4 · Google Ads · Meta

  6. Signs and print

    Posters, flyers, name cards and the signs on site come from the same price data as the site, so print never disagrees with it.

    Built with React · Playwright · PDF

  7. Security, and the day something breaks

    Every change goes live only after tests and automated checks pass. The database is locked down row by row, and there are written steps and spares to bring the on-site PC back if it dies.

    Built with GitHub Actions · Playwright · semgrep · gitleaks · Sentry

    The site monitor’s topology: the internet, the gateway, the recorder, cameras, sensors and Wi-Fi on one diagram
    The site monitor, as it runs

In numbers

3,030
changes shipped since December 2025
85
server functions
964
database migrations
7
cameras on one screen

As of 2026.10.30, counted from the code.

Enter money once

I used to type the same money into three apps.

  1. Tsumagoi Work&Camp

    Sales, payouts, stock and the daily close. It writes accounting batches at each close and every night.

  2. Solo Boss Cloud (一人社長)

    Pulls those batches every hour and books them as draft journal entries. Nothing reaches the ledger until they are approved.

  3. yen-yen

    Sends business costs paid on a personal card to Solo Boss Cloud as 立替 claims, and gets their status back.

We can build this kind of link between your apps.

Other things we built

  • Solo Boss(opens in a new tab)

    Bookkeeping through to tax filing, for one-person companies

    This place's accounting flows in here as draft journal entries.

    solo-boss-cloud_backend 一人社長 (Solo Boss Cloud) — AI legal, tax & accounting advisor for Japanese solo entrepreneurs. Backend API: Express 5 + Prisma + Supabase/PostgreSQL, multi-LLM (OpenAI/Claude/Gemini), NTA/e-Tax/eLTax integrations.

    solo-boss-cloud-documentation 一人社長 (Solo Boss Cloud) — AI accounting & tax advisor for Japanese solo entrepreneurs. Frontend: React 19 + Vite + Tailwind PWA (also iOS/Android via Capacitor).

    Read the story(opens in a new tab)

  • yen-yen(opens in a new tab)

    A shared household money book, no bank login

    Business costs paid personally go from here to Solo Boss Cloud.

    yen-yen kakeibo-inspired cloud budgeting app for iOS, Android, and the web

    Read the story(opens in a new tab)

  • Mushi Mushi(opens in a new tab)

    A report-a-bug button for apps, with AI that sorts the reports

    mushi-mushi Know why your AI-built app broke — plain-English diagnosis + ready fix, in your editor. Open source. Sentry optional.

    Read the story(opens in a new tab)GitHub(opens in a new tab)

  • glot.it(opens in a new tab)

    A Thai learning app with an AI tutor

    glot.it Learn Thai with AI — music, conversations, podcasts, 161 structured lessons, speech feedback & FSRS spaced repetition. Web PWA + iOS + Android (Capacitor).

    Read the story(opens in a new tab)

What we can build for you

The first 30-minute call (online) is free. We price the work once we know what it is.

  1. Booking and payment sites

    Live availability, online payment (card, Square, PayPay), Japanese and English, and the confirmation mail.

  2. AI chat and auto-replies

    On your site, LINE or a tablet at the counter: answers from your own price list and rules, and hands the rest to a person.

  3. Cameras and sensors on one screen

    The same system as our site monitor, for your place. The terms of a pilot are being set now; ask us.

  4. Advice for small places

    For small inns, coworking spaces and campsites: the booking flow, ad measurement, listings and automating the daily work.

We also upgrade old PHP systems without switching them off(opens in a new tab)Visit kensaur.us(opens in a new tab)

Partners and investors

We welcome people who want to take this system to other places, and conversations about investing or partnering.

Press and posts

Writing about this place and how it was built.

More on note and Zenn: note · Zenn

Questions

Who built the Tsumagoi Work&Camp system?
Sennin Kenji (Kenji Sakuramoto, representative of Kensaurus LLC), who runs the place, designed, built and runs it alone: booking and payments, the AI chat, the kiosk at the door, the camera and sensor monitor, and the signs and print.
Can kensaurus build a booking site or a camera dashboard for my place?
Yes. We build booking and payment sites, AI chat, and screens that put cameras and sensors on one plan for small inns, coworking spaces, campsites and similar places. The terms of a site-monitor pilot are being set now. Start by telling us about your place.
How do I get in touch about a project?
By email (kensaurus@gmail.com); there is no phone. Tell us about the place, what you want to change and by when. The first 30-minute call (online) is free; a site visit is by arrangement, with travel costs charged.
Can you connect my booking, accounting and expense apps so money is entered once?
Yes. Tsumagoi Work&Camp writes accounting batches at each close and every night; Solo Boss Cloud pulls them every hour and books them as draft journal entries. Business costs paid personally go from the yen-yen money app as claims, and their status comes back. We build the same kind of link between your apps.
Are you open to partners or investors?
Yes. If you want to take this system to other places, help build places like this one, or are thinking about investing or partnering, we would like to hear from you.

Get in touch

Email us about your place and what you want to change. A word on where you found this page helps us too.

Email uskensaurus@gmail.com

The first 30-minute call (online) is free. A site visit is by arrangement, with travel costs charged. There is no phone.

The place itself:HomeInstagram(opens in a new tab)Guest questions on LINE(opens in a new tab)

Sennin Kenji waving hello

Even up a mountain, you wire it one cable at a time. — Sennin Kenji