Paste the text of a letter from a Japanese city hall and see what it is, the deadline, the amount and what you have to do, in English or Simplified Chinese.
Everything runs in your browser with plain rules. No AI model, no server, no account, and nothing you paste leaves your device, which matters because these letters carry your name, address and sometimes your My Number.
Try it: https://yema7582-code.github.io/oshirase/ (tap one of the sample letters)
- Recognises common letters: National Health Insurance, resident tax, pension, My Number card, residence card, property and light-vehicle tax, child allowance, check-ups, vaccinations, and overdue reminders (督促状).
- Finds the deadline among all the dates in the letter and converts Reiwa dates (令和8年10月31日, R8.11.6) into a normal date with a countdown.
- Finds the amount to pay and writes a one-line to-do: pay, send back, go to the counter, or renew your stay.
- Lists what to bring, the office to contact and tap-to-call phone numbers.
- Shows the letter with furigana over about 100 bureaucratic words. Tap one to see its meaning.
- Turns red for overdue notices and close deadlines.
- Downloads the deadline as a calendar event with a reminder the day before.
Requires Node.js 18 or newer (only for the tiny static server and the tests; the app itself has no dependencies).
npm start # http://localhost:5173
npm test # 13 unit tests with node:test
Handy URL options: ?sample=nhi|mynumber|overdue opens a sample, ?lang=zh starts in Chinese, ?today=2026-10-20 pins today's date.
Planned and built with the Devpost Learn skill pack and an AI coding agent for the Build With AI: Basics hackathon. The planning documents are in devpost/: scope, PRD, spec and the build checklist.
Start reading the code at src/parse.js > analyze(). Everything the page shows comes from the object it returns.
Oshirase explains the letter; it is not tax or legal advice. Letters differ between cities, so if the page finds no deadline, look for a date next to 期限 or まで and call the number on the letter. The sample letters are made up.
MIT