kensaurus

Work with us · as of 30 October 2026

We run a mountain site on our own software. We can build yours.

kensaurus LLC built the booking and payments, the AI chat and the camera and sensor screens behind Tsumagoi Work&Camp in Tsumagoi, Gunma, and uses them every day. We take on development and consulting from that experience.

What we build for you

  1. Booking sites, payments and admin consoles

    A site where guests see availability and prices, then book and pay in one go. Payments by Stripe, Square or PayPay. A console that shows bookings, the shop and the Wi-Fi in one place. Japanese and English, phone first.

  2. AI chat for your website, LINE and front door

    An AI that answers from your own facts, on your website chat, your LINE official account, and a tablet or voice at the entrance. It answers the late-night questions so you don't have to.

  3. Camera and sensor dashboards

    Security cameras, temperature and power sensors, the door and the network, on one screen. We start by checking whether the equipment you already have can do the job.

  4. Consulting for small inns, campgrounds and coworking spaces

    Booking, payments, an unstaffed front door, and marketing and measurement for places with no one at the desk. First we sort what your current tools already cover from what is worth building.

  5. Legacy PHP upgrades

    We bring a running PHP system up to date one step at a time, without switching it off.

    How we run an upgrade · php2shell response

  6. Ranch Monitor pilot

    The control screen we use ourselves: cameras, sensors, the door and the day's bookings on one floor plan. We are getting ready to pilot it with a few small sites. The terms are still being set, so there is no price yet. If you are interested, ask.

    Read the Ranch Monitor story

We quote after we hear what you need (the first 30-minute call is free; see Contact).

Case study: Tsumagoi Work&Camp

Tsumagoi Work&Camp is a 24-hour lounge on the mountain, 1,444 m up in Tsumagoi, Gunma. You sleep in your own car or a tent. It opened on 8 August 2026. Every system that runs it, from booking to the front door and the cameras, was built and is run by one person: the founder, Kenji Sakuramoto (Sennin Kenji), working with AI coding assistants.

The Ranch Monitor. In the centre, a floor plan of the site with each room's temperature, the seven cameras drawn where they hang with their latest pictures, and the power drawn by the kotatsu and the vending machine. On the right, a short list of things to check, the weather, the water tank and today's guest groups
The Ranch Monitor, with any camera showing a person hidden (30 October 2026). The interface is in Japanese.
Booking site
Japanese and English. React 19, TypeScript, Vite and Tailwind; data in Supabase in the Tokyo region; served from AWS (S3 and CloudFront). Installs on a phone like an app (PWA).
Payments
Stripe, Square and PayPay, each with its own payment flow and webhook.
Admin console
Bookings, the shop, Wi-Fi, cameras, and the ad and analytics numbers in one place.
AI answers
In four places: the website chat, LINE, the entrance tablet's voice and the voice at the door. It answered 492 questions in October.
Front-door kiosk
A PWA on an Android tablet at the entrance that updates itself over the air.
Ranch Monitor
Seven cameras with AI detection of people, cars and animals (no face or plate reading), temperature, weather, power, the water tank and the network, on one floor plan, with a 24-hour replay.
Signs and print
Posters, flyers, business cards and signs generated from one price source, so a price change updates all of them.
Ads and analytics
GA4, Google Ads and Meta. A conversion counts once, on a real booking.
Automated checks
GitHub Actions on every change: secret scanning, dependency audit, database permission checks, drift checks, browser and accessibility tests (Playwright, WCAG) and static analysis (semgrep), on self-hosted runners.
Security and recovery
Row-level security in the database, a secret scan of the whole history, CSP and OWASP-based rules. A restore kit for the on-site PC and nightly backups.
Staff alerts
Five Discord channels, one per kind of job.

By the numbers (30 October 2026)

300+
UI components
80+
server functions (edge functions)
960+
database migrations
230+
pages
2,900+
commits since 18 December 2025
492
questions the AI answered in October

Enter money once

Kenji used to type the same money into three apps. Shop sales, payouts and stock lived in the Tsumagoi Work&Camp system. The books lived in Solo Boss. Business costs paid from a personal card went into yen-yen, and then again into Solo Boss as a reimbursement claim. Now each money fact is entered once, and the apps hand it on to each other.

On siteTsumagoi Work&CampSales, payouts, stock and the daily close
C1 accounting batchesat each close and nightly
The booksSolo Boss Cloud (一人社長)Pulls them hourly as draft journal entries. Nothing reaches the ledger until the owner approves
C2 reimbursement claimsC3 claim and payout status
Personal moneyyen-yenBusiness costs paid from a personal card
How the three apps link up (C1, C2 and C3 are the contracts between them)
Tsumagoi Work&Camp
Sales, payouts from the payment providers, stock and the daily close live here. It writes accounting batches when a period is closed, and again every night (C1).
Solo Boss Cloud
Pulls those batches every hour and books them as draft journal entries. Nothing reaches the ledger until the owner approves the batch.
yen-yen
Sends business costs paid from a personal card to Solo Boss as reimbursement (立替) claims (C2), and gets the claim and payout status back (C3).

We can build this kind of link between your apps.

Writing

How we built it, and what running it taught us. Most posts are in Japanese.

Other things we build and run

Also kenji skills, step-by-step instructions for AI coding assistants (open source), and more. Everything is in the exhibit hall, and the company facts are on the press page.

FAQ

Who built the Tsumagoi Work&Camp system?

Kenji Sakuramoto (Sennin Kenji), the founder of kensaurus LLC, built it on his own with AI coding assistants, and runs it. That covers booking and payments, the admin console, the AI chat, the front-door kiosk, and the camera and sensor screens.

Can kensaurus build a booking site or a camera dashboard for my place?

Yes. Booking and payments (Stripe, Square, PayPay), AI chat including LINE, and one screen for your cameras and sensors, sized to your place. We start by checking what your current equipment and tools can already do.

How much does it cost?

The first 30-minute call, online, is free. Site visits are by arrangement, and we charge travel costs. Anything else we quote after we hear what you need. Terms for the Ranch Monitor pilot are still being set.

Can you upgrade an old PHP system?

Yes. Without switching it off: an inventory, urgent fixes, behaviour tests and a rehearsed rollback, then upgrades one stage at a time. The "How we run an upgrade" page has the detail.

Do you work with clients outside Tokyo or outside Japan?

We take on work in Japan, and meetings can be online, in Japanese or English. If the job needs on-site work such as installing equipment, tell us where and we will talk it through.

How do I contact kensaurus about a project?

By email, to kensaurus@gmail.com, with "[Work inquiry]" in the subject. Tell us what you want to build, where and what kind of business, and where you found this page.

Are you open to partners or investors?

Yes, we are happy to talk. Use the same contacts.

For partners and investors

If you are a company, a local government or a person interested in Tsumagoi Work&Camp or our products, we would be glad to talk. An early "we might want to do something together" or "we are thinking about investing" is fine. The contacts are below.

Contact

We take work inquiries by email. A line or two is enough: put "[Work inquiry]" in the subject and tell us what you want to build, where and what kind of business, and where you found this page.

Emailkensaurus@gmail.comOpens with the "[Work inquiry]" subject and three short questions.
First call30 minutes, freeOnline. Site visits are by arrangement, and we charge travel costs.

There is no phone line. Tsumagoi Work&Camp's LINE account is for its guests; please send work inquiries by email.