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Privacy Policy for Usagi

1. Introduction

This Privacy Policy explains how the Usagi application ("we," "us," or "our"), an app for learning Japanese, handles your data. We are committed to protecting your privacy.

Usagi is designed to work on your device. We do not run servers that receive your data, and we do not track you across apps or websites. The free version of Usagi shows ads provided by Google AdMob, described in section 5. Subscriptions are handled as described in section 4.

2. Information Stored on Your Device

To teach you and track your progress, Usagi keeps the following on your device only:

  • Learning progress: the characters, words, kanji and grammar you have met, your answers and review schedule, lesson stars, experience points, streaks and badges.
  • Profile choices: the name you enter (optional), and the avatar and background colour you pick.
  • Setup answers: the birthday, Japanese experience and learning goals you give when you first open the app, used to tailor your starting point.
  • Settings: interface language, writing style, sound effects and reminder time.

None of this is sent to us or to any third party. It may be included in your device's own backups (such as iCloud Backup on iPhone, or Google's backup on Android) if you have those turned on; those backups are handled by Apple or Google under their own privacy policies.

3. Reminders

If you turn on daily reminders, Usagi asks for permission to send notifications and schedules them on your device. Reminders are local notifications: they are not sent from a server, and no notification data leaves your device. On Android, Usagi keeps the week's reminders on your device so it can set them again after your phone restarts. You can turn them off in the app's Settings or in your device's notification settings at any time.

4. Subscriptions and Payments

Usagi offers an auto-renewable subscription. Payments are processed by the Apple App Store on iPhone and by Google Play on Android. We do not collect, store, or have access to your payment card or billing details; Apple and Google handle these under their own privacy policies.

We use RevenueCat to manage subscriptions: to check whether your subscription is active and to restore purchases on a new device. To do this, RevenueCat receives:

  • An anonymous app user ID generated by the app, which is not linked to your name, email, Apple Account or Google Account.
  • Your purchase and subscription history for Usagi, as reported by the App Store or Google Play.
  • Basic device and app information, such as device model, operating system version, app version, and country or region.

RevenueCat does not receive your learning progress, profile or setup answers. You can read RevenueCat's privacy policy here: RevenueCat Privacy Policy

5. Advertising

Free users see full-screen ads from Google AdMob between lessons and practice sessions. Usagi Pro subscribers see no ads.

Usagi does not ask to track you and does not use your device's advertising identifier. Ads are non-personalised and limited to content suitable for all ages. For learners whose birthday shows they are under 13, ad requests are marked as directed to children; for those under 16, as under the age of consent.

To serve and measure ads, Google receives device and app information (such as device model, operating system version and app version), an approximate location derived from your IP address, how you interact with ads, and diagnostic data. On Android it also receives the app set ID, an identifier Android shares only among apps from the same developer on your device; it is not the advertising ID. It does not receive your learning progress, name or birthday. See Google's Privacy Policy and how Google uses information from apps that use its services.

Where the law requires it (for example in the EEA and UK), Usagi asks for your consent through Google's consent form, and you can change your choice at any time in Settings → Privacy choices. Usagi contains no analytics of its own, and we do not sell your data.

6. Keeping and Deleting Your Data

Everything Usagi stores is kept on your device until you delete the app. To delete your Usagi data:

  1. Your learning data: delete the Usagi app from your device. This removes your progress, profile, setup answers, settings and reminders, which are stored nowhere else.
  2. Your subscription record at RevenueCat: email usagi.app@starsynthesis.org with the subject "Delete my Usagi data", and include the order number from your App Store or Google Play receipt so we can find it. We delete the record and confirm by email.

Apple and Google keep their own records of your purchase, under their privacy policies, and Google keeps advertising data under Google's. We cannot delete those for you; your Apple Account or Google Account settings let you manage them.

7. Children's Privacy

Usagi asks for your birthday during setup only to tailor the experience, and it stays on your device. We do not knowingly collect personal information from children under 13, and because Usagi sends no personal information to us, we hold none to delete. Children's ad requests are marked as child-directed, as described in section 5. If you are a parent or guardian with questions, please contact us.

8. Credits

Usagi is built on the generous work of these projects. Their licences require the credits below.

  • Voice: VOICEVOX:WhiteCUL. Japanese audio generated with VOICEVOX using the WhiteCUL voice (terms of use).
  • Vocabulary: JMdict/EDICT, © Electronic Dictionary Research and Development Group, used under CC BY-SA 4.0 (EDRDG licence).
  • Kanji readings and meanings: KANJIDIC, © Electronic Dictionary Research and Development Group, used under CC BY-SA 4.0, via kanji-data by David Gouveia (MIT).
  • JLPT levels: © Jonathan Waller, tanos.co.uk, used under CC BY.

Usagi's word and kanji data are adapted from JMdict and KANJIDIC, and those adaptations are shared under the same CC BY-SA 4.0 licence.

9. Changes to This Privacy Policy

We may update this Privacy Policy from time to time. Any changes will be posted on this page with a new date below, so please review it periodically.

10. Contact Us

If you have any questions or suggestions about this Privacy Policy, contact us at usagi.app@starsynthesis.org

Last updated: October 11, 2026.