About kensaurus LLC

What the company does

kensaurus LLC is a small company founded in Shibuya, Tokyo, in June 2025. Starting from everyday problems, it builds apps and runs them itself: a household money book, bookkeeping and tax filing for one-person companies, Thai lessons, a camera for taking each other's photos, and a place to practise a hard reply. The founder builds them almost alone, with AI coding assistants.

Since 8 August 2026 it has also run Tsumagoi Work&Camp, a campground you can work from, on a former ranch 1,444 metres up in Tsumagoi, Gunma. The software behind it, from the booking site and payments to the screen that shows the weather on site, is the company's own.

The name joins "Ken" and "saurus", the ending of many dinosaur names. Like a fossil, the aim is to make things that are still useful after their trend has passed, starting with ten years.

What it does, in four parts

1. Its own apps and web servicesApps for everyday life and work. Five are live on both the App Store and Google Play (listed below).
2. Open-source tools for developersMushi Mushi, which sorts users' bug reports with AI, and kenji skills, written procedures for AI coding assistants. Both are free to use.
3. Tsumagoi Work&CampA campground and share office on a former ranch in Tsumagoi, Gunma. The disused building took a year to renovate.
4. Development workWeb and app development, upgrading old PHP systems without switching them off (how it works), and advice on putting disused buildings back to use.

Tsumagoi Work&Camp

The founder, Kenji Sakuramoto, lived in Singapore for more than 20 years and moved back to Japan about two years ago. He took up camping and climbing, which meant driving out of Tokyo every weekend and sitting in traffic all the way back. So he decided to build a place where you can work and camp at once.

He found a former ranch 1,444 metres up in Tsumagoi, Gunma. Tsumagoi Bokujo, once known for its milk and ice cream, had closed after COVID, about six years earlier. On the first visit in August 2025, the chairs in the hall were still stacked on the tables. Over about a year he and his wife cleaned it out, put in double glazing, heating and air conditioning, and on the coldest nights slept in a tent pitched inside the building so they could keep working. The old hall is now a share office with fibre internet. It opened on 8 August 2026. It is a separate business from the old ranch and does not sell its milk or ice cream.

• What it is: a campground with no marked plots, where you stay in your own tent or car. There is a share office with fibre internet (100 Mbps), hot showers and a shared kitchen. Nobody sleeps inside the building.
• Who it's for: people who want to work in nature, away from the city, or simply have time to do nothing. The operator says there are no homes within 7 km, so on days with no other guests one group can book the whole place, events included.
• A typical day: crawl out of the tent, take a video call from the share office, light the fire pit in the evening, look at the stars at night.
• Status: open Thursday to Monday (a Tuesday or Wednesday arrival is arranged on LINE). Prices and booking are on the camp's own site.

The place name Tsumagoi (嬬恋) means "loving your wife".

Main products

Status checked on 23 October 2026. "Live" means anyone can use it; "prototype" means it was built as an experiment and is public.

• Tsumagoi Work&CampOpen

  A mountain campsite with an office, run by us

  Tsumagoi Work&Camp is a campground at 1,444 m in Tsumagoi, Gunma, on a former ranch with no houses within 7 km. Guests pitch a tent anywhere on the field, work from an office on fiber internet, and end the day by the fire. We renovated the buildings ourselves, built most of the furniture on site, and opened in August 2026. The website, online booking, payments and on-site sensors are all software we wrote.

  • Book a tent pitch, a car-camping spot or an office day pass online
  • Work on fiber internet, with a kotatsu room for the cold months
  • Check the live weather at the camp, or ask the AI concierge any time

• Mushi Mushi (虫虫)Live · beta

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

  Error-tracking tools only notice problems that crash the app. Mushi Mushi catches the ones people notice, like a button hidden behind a header, by adding a small report-a-bug button to any website or app. AI rates each report, groups duplicates and points to the likely cause in the code, and it can draft a fix for a developer to approve. It is open source, with a free hosted plan.

  • Users write one line; the screenshot, page and technical details are attached for them
  • AI rates how serious it is, merges duplicates and names the likely file
  • Fixes arrive as drafts, and a person decides whether to merge them (automatic merging is an option, off by default)

• Solo Boss (一人社長)Live · free for now

  Bookkeeping, year-end accounts and tax filing for one-person companies

  A web workspace for people who run a company alone in Japan. It covers the daily books, the year-end statements and the files you file with the tax office and the local government, on one screen. The AI drafts and the owner confirms; the owner submits through the government's e-Tax software. Every feature is free for now.

  • AI drafts journal entries from bank lines and receipts
  • More than 30 checks before filing; balance sheet, income statement, Schedule 4 and e-Tax / eLTAX files from the same numbers
  • Send your tax accountant a review link with an expiry date and a password

• kenji skillsLive · free

  Step-by-step playbooks that keep AI coding assistants on track

  AI coding assistants such as Claude Code, Cursor, Codex and Gemini often stop halfway, or say a job is done when it is not. kenji skills is a free, open-source set of written procedures they follow step by step, from fixing a bug to shipping a release, and a separate AI checks that the work is really finished. We use it on every project we run, and it installs with one command.

  • Ask in plain words, like “fix this bug and ship it”, and the matching playbook runs
  • A separate reviewer compares the plan, the changes and fresh test results before “done”
  • One npx command installs it for Claude Code, Cursor, Codex and Gemini

• yen-yenLive

  A shared household money book, no bank login

  yen-yen is a household money book that two people, or a whole family, keep together. It never asks for your bank login: add spending by hand in a few seconds, or paste a bank statement and AI sorts the lines for you to check before anything is saved. Four simple categories show where the money went by the end of the week. It runs on iPhone and Android.

• glot.itLive

  A Thai learning app with an AI tutor

  glot.it teaches Thai to people starting from zero, whether for a trip, a Thai partner or family, or work. It covers the Thai script, the five tones and everyday speaking, with an AI tutor you can talk to. It runs in the browser and on iPhone and Android.

• help her take photoLive

  Two phones, one camera: the person in the photo directs the shot

  help her take photo links two phones. One is the camera, and the other shows that camera’s view live, so the person being photographed can see the shot and direct it before it is taken. It is made for couples and friends who travel together, on iPhone and Android.

• lets-talkLive

  Practise difficult conversations with an AI coach

  lets-talk helps you work out what to say when a message is hard to answer, from an upset boss, partner or friend. Paste their message to see their side and get replies you could send, write your own reply and get it scored, or rehearse the whole chat with an AI that plays the other person. On iPhone, Android and the web, with no account needed. It is a practice tool, not therapy.

• the wanting mindLive

  A book about why we want, free to read online

  Why do people want, and why do some take while others give? the wanting mind is a 36-chapter book by our founder that follows that question through neuroscience, economics, philosophy and anthropology. It is free to read on the web and in the iPhone and Android apps.

• Skin AnalysisLive · free

  Skin scores and care tips from one selfie

  Take one selfie in natural light and get scores for more than 20 skin concerns, such as pores, hydration and texture, plus 4 to 6 care tips. Claude reads the photo. It is free, needs no account, and the photo is deleted after the analysis.

• Hear, HearPrototype · free

  Live transcription in your browser, no account

  Hear, Hear turns speech into text while people talk, right in the browser. Every line keeps its timestamp, and tapping a line replays that moment. There is no account, and recordings stay in your browser. In this public version a recording can run up to five minutes. Live transcription uses the browser's own speech recognition, so in Chrome your voice goes to Google's speech service.

• KontePrototype

  Plan and make an 8-second AI video, step by step

  Konte (Japanese for storyboard) walks you through a short AI video the way a film crew works: pick a template, write the scene, choose the camera and mood, review, then render. Google’s Veo makes the video with your own Gemini API key, so Google bills you directly and Konte charges nothing. It is a prototype, first built for our partner babuu AI.

Other prototypes and finished one-off pieces are in the exhibit hall.

In numbers

6 June 2025

The company was founded

5

Apps live on both the App Store and Google Play (23 October 2026)

8 Aug 2026

Tsumagoi Work&Camp opened

1,444 m

Altitude of Tsumagoi Work&Camp

The founder

Kenji Sakuramoto (櫻元 賢次)
Representative, kensaurus LLC

Lived in Singapore for more than 20 years and moved back to Japan about two years ago. Founded kensaurus LLC in Shibuya, Tokyo, in June 2025. Builds and runs apps that began with problems in his own life or the lives of people near him, almost alone, with AI coding assistants. Keeps his own company's books and filing in his own app, Solo Boss, with a tax accountant checking. In August 2026 he and his wife opened Tsumagoi Work&Camp on a former ranch they renovated in Tsumagoi, Gunma.

As a young man he found talking to people hard, and it took him years to understand what people really meant. Meeting people from other countries changed that, and the experience led to the conversation-practice app lets-talk (in his own words).

Photos and screens

You may use these photos and screens to report on the company. Tap an image to open the larger file. For higher-resolution photos, or a photo of the founder, please get in touch.

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  The meadow, morning
  Photo · 1600×1200

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  Tent and fire pit, autumn
  Photo · 1600×1200

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  Winter sunset
  Photo · 1600×1200

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  Solo Boss, year-end close
  Screen · fictional sample company

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  yen-yen, the week
  Screen · sample household

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  help her take photo
  Store screen (the people and scene are generated)

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  glot.it lessons
  Screen

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  Mushi Mushi console
  Screen · reports on the company's own apps

Credit: kensaurus LLC

Company facts

Name

ｋｅｎｓａｕｒｕｓ合同会社 (kensaurus LLC)

Representative

Kenji Sakuramoto (櫻元 賢次)

Founded

6 June 2025

Capital

¥1,000,000

Address

Shibuya Dogenzaka Tokyu Bldg. 2F-C, 1-10-8 Dogenzaka, Shibuya-ku, Tokyo 150-0043, Japan

Corporate number

5011003021894

Invoice registration

T5011003021894

Business

Building and running apps and web services, publishing developer software, running a campground and share office (Tsumagoi Work&Camp), development work

Website

https://kensaur.us/

Tsumagoi Work&Camp

2401-615 Hoshimata, Tsumagoi, Agatsuma District, Gunma 377-1611, Japan · https://tsumagoi.kensaur.us/en/