Privacy Policy — Jishin Sensei
Last updated: October 15, 2026
Jishin Sensei ("the app") is developed and operated by Makoto Katano.
The short version
The app has no accounts, no ads, and no analytics or advertising SDKs. It never asks for your name, email address or location, and nothing you type into it is sent to the developer or to any server. Two services receive limited technical data so the app can work: Expo, to deliver content updates, and RevenueCat, to handle tips. Details below.
The website's contact form is separate from the app: it receives only what you type into it. See Contact form below.
What stays on your device
Your quiz answers, streak, and preferences are stored only on your device. They are never uploaded to any server, and deleting the app deletes them.
Your health card and trip card are kept in the Keychain of your iPhone or iPad. They are never sent to the developer or to any server, and they are not synced with iCloud Keychain. Like other Keychain items, they can be included in an encrypted backup of your device and restored to a new device from that backup. iOS and iPadOS keep the Keychain even after an app is deleted, so if you reinstall the app on the same device, the cards come back. To erase them, tap "Clear this card" at the bottom of each card in the app before deleting the app.
If you save a card as an image, it goes to the Photos app. It stays there after the app is deleted, and with iCloud Photos on it also syncs to your other devices.
Content updates (Expo)
When it starts, the app asks Expo's update service (EAS Update) whether new content is available, and downloads it if so. Each request carries a random identifier that the app creates for this purpose (it is deleted with the app), the app's version and update IDs, and the platform (iOS). Like any server, Expo also sees your IP address.
- Expo's privacy policy: https://expo.dev/privacy
In-app purchases
Tips are processed by Apple through the App Store. To handle them, and to restore a Supporter unlock bought in an earlier version, the app uses RevenueCat, a purchase-management service. While the app runs, RevenueCat receives a randomly generated anonymous identifier; the identifier Apple gives this developer's apps on your device (identifierForVendor, not the advertising identifier); basic device and app information (device model, OS version, app version, preferred languages and App Store country); and, if you leave a tip, the App Store receipt. The developer sees tip totals, including where in the app each tip was offered. RevenueCat does not receive your name, email address, Apple Account or any contact information from us.
- RevenueCat's privacy policy: https://www.revenuecat.com/privacy
External links
The app links to official public-safety resources (such as the Japan Meteorological Agency, the Japan National Tourism Organization, and mobile carriers' alert-sound demonstration pages). When you open those links, the respective sites' own terms and privacy practices apply. The app is independent and is not affiliated with or endorsed by any of these organizations.
Emergency information disclaimer
The app's safety content is educational and based on the sources it cites, mostly Japanese public agencies. In an actual emergency, always follow instructions from local authorities.
Contact form (website)
The website has a contact form, run on Google Forms. It is separate from the app — the app itself never asks for your name or email address.
- What we receive: what you type into the form — the topic, your email address and your message, and, if you choose to give them, your name (you may stay anonymous), your requests, your property or company name, and how you heard about the app.
- What we use it for: only to reply to you and to improve the app. We do not add you to a mailing list, and we do not share or sell it.
- Where it is kept: in Google Forms and Google Sheets under the developer's Google account. Google handles it under its own privacy policy: https://policies.google.com/privacy
- How long: deleted within 12 months after our last exchange, or sooner if you ask.
- Deletion: reply to any email from us, or ask through the form.
Changes
If this policy changes, the updated version will be posted at this page with a new "Last updated" date.
Contact
Questions about this policy: please use the contact form.