Press & Media
Jag's Kairanban-app is a free, open-source web app (PWA) for Japan's neighborhood associations (chōnaikai), developed and published by Jag Project, LLC as a flagship project to test what "digital self-governance" can look like in the age of generative AI. It digitizes the kairanban — the paper circular board that has been passed from door to door in Japanese neighborhoods for decades. For interview requests and materials, please use the contact below.
Contact
Email: press (at) jagproject.com (Jag Yamamoto)
Based in Koto ward, Tokyo. Live demos and remote interviews available. Interviews are most comfortable in Japanese; English inquiries are welcome.
For citation terms for figures and images, see the Citation Guide at the end of this page.
Fact Sheet
Split into two groups: what it took to build, and what it costs an association to run.
Development effort and cost
| Time to beta | About 2 weeks from first prompt to public beta. Updated daily since, including contributions via GitHub |
|---|---|
| Code size | About 10,000 lines of TypeScript |
| Database migrations | 23 |
| Development cost | Mainly paid subscriptions to generative AI tools (ChatGPT and Claude). Setting aside labor, that was the principal expense |
| Measured, not assumed | On iPhone, the iOS share sheet leaves the top 42.7% of the screen visible — measured on real devices. The entire install guide was designed to fit inside that band |
Numbers for an adopting association
| Running cost | From ¥0/month (Cloudflare free tier). The person who sets it up and adapts it will, in practice, need a paid generative-AI coding tool |
|---|---|
| Languages | 5 — Japanese, Easy Japanese (yasashii nihongo), English, Chinese, Vietnamese |
| License | MIT — free to modify and use commercially |
Note: figures and images may be quoted with attribution to kairanban.jagproject.com.
The story in one paragraph
In the country that recently declared victory in its "war on floppy disks," another analog institution survives: the paper kairanban, a clipboard of notices that takes a week or more to circle a neighborhood. An active neighborhood-association officer — who had produced and directed software projects for years but had not written code since BASIC in junior high school — directed a generative AI (Claude Code) to build a replacement, reached a public beta in about two weeks, and released it as free open source. Electronic circular boards are becoming a market in Japan, mostly as monthly subscriptions that drain association fees out of the community. This app is designed the other way around: it runs on free-tier infrastructure, and if anyone is paid to maintain it, it can be the association's own IT-literate members or local businesses — so the money circulates inside the neighborhood. The developer proposed it to his own association in Koto ward, Tokyo, and is now recruiting the first partner association to test it in real use. Every failure along the way — including a 20-out-of-100 score for the first onboarding guide — is published.
Background for reporters: the kairanban, briefly
What it is
A kairanban is a clipboard of printed notices — festival dates, garbage-sorting rules, disaster-drill schedules — passed by hand from house to house. Each household reads it, stamps its personal seal (hanko) or signs, and walks it to the next door. A full circuit of a neighborhood can take a week or more.
Where it came from
The kairanban is a wartime institution that outlived the war. Tokyo distributed 100,000 kairanban boards in 1939; a Home Ministry ordinance of September 1940 organized every city block into neighborhood associations and ten-household units (tonarigumi), with the kairanban as their official channel. A national radio song of 1940, "Tonarigumi," even told citizens to "pass the kairanban along" — the object is embedded in Japanese popular memory. The wartime structure was dissolved after 1945, but the clipboard stayed, and it still circulates through neighborhood associations across Japan today.
Why it has survived the smartphone
The kairanban does three things no ordinary app does. It reaches every household, regardless of technology. The handover doubles as a doorstep check on aging neighbors — if the board stops moving, someone notices. And it is a small ritual of contact in a society worried about isolation. Digital replacements that serve only the young abandon exactly the people the kairanban exists for. That is a large part of why it is still here.
The point of this project: preservation, not disruption
Jag's Kairanban-app is not an attempt to abolish the kairanban. It is an attempt to preserve what the kairanban does — reach everyone, confirm who has seen a notice, keep the sense of being looked after — in a form that can survive the next decade. The design consequences are concrete: an install guide built for members who are not comfortable with smartphones (nothing to memorize, measured on real devices), read-confirmation lists that replace the hanko stamp, and five languages so that foreign residents — the newest neighbors — are inside the circle, not outside it.
This is not a disruption story. It is a rescue operation for a paper institution, teaching a system born in 1940 to send push notifications.
Why now: the closing window
The officers running Japan's neighborhood associations today — largely in their 40s to 60s — are the country's analog-digital hybrid generation: people who used PC-9800s and Macintoshes at work and passed paper kairanban at home. They are the last cohort fluent in both worlds, and they know exactly what the paper board does for a community. If the handover from paper to digital is going to preserve the institution rather than lose it, it has to happen on their watch. That is the deadline this project is built against.
Profile
Jag Yamamoto
Representative of Jag Project, LLC (Tokyo), and an active officer of his local neighborhood association. After a career in product planning and business development in Japan's media and entertainment industry, he now runs 0-to-1 business development projects. Part-time lecturer at Musashino Art University. He has written on community IT use for Japanese media (BCN, 2024). The full development record — including failures — is published at "The Dev Story (English)".
FAQ
Q: It is free. How does it sustain itself?
A: The app is free, with no plans to charge. Jag's Kairanban-app is our verification project: what we gain is first-hand knowledge of AI-era software development and of "digital self-governance" in practice.
Q: What about personal data?
A: Each association hosts its own member data on its own (free-tier) infrastructure; we hold none of it. Members join with the association's approval, and the app deliberately has no feature for members to connect one-to-one. Before publication, we ran optical character recognition over all 33 published images and machine-checked them against the database — zero instances of personal data.
Q: Why give it away?
A: A circular board that keeps association fees inside the community can only exist as free open source. We want associations across Japan — and anyone facing similar problems elsewhere — to use it freely and keep the know-how local.
Citation Guide
- Figures and images from this site and "The Dev Story" may be quoted with attribution to "Jag's Kairanban-app (kairanban.jagproject.com)".
- Screenshots may be used for news reporting.
- The demo runs on fictional data and may be filmed or captured. It resets every 24 hours.
- For any other materials, email the address above.