🎌 Japanese Sensei

1. Overview

Japanese Sensei ("the App") is a Japanese language learning application designed for Vietnamese workers living in Japan. We are committed to protecting your privacy. This policy explains what information the App handles and how.

Effective date: April 4, 2026

2. Information We Do NOT Collect

Japanese Sensei does not collect, transmit, or store any personal information on external servers. We do not collect:

• Name, email address, or phone number
• Device identifiers or advertising IDs
• Location data
• Usage analytics or crash reports sent to our servers
• Any data that identifies you personally

3. Data Stored Locally on Your Device

The App stores the following data only on your device using AsyncStorage. This data never leaves your device:

• Learning progress – which words and phrases you have marked as mastered, per category
• Study streak – consecutive study days count and last study date
• Notification setting – preferred daily reminder hour (e.g. 19:00)
• Onboarding status – whether you have completed the intro screens
• Level onboarding status – whether you have seen each level's tutorial

4. Push Notifications

The App may request permission to send local push notifications as daily study reminders. Notifications are scheduled entirely on your device using Expo Notifications. No notification data is sent to our servers. You can disable notifications at any time in the App settings or in your device's system settings.

5. Optional Cross-Device Transfer (Anonymous)

The app does not require account creation, sign-in, or any personal information. You can use all features without providing your name, email, phone number, or social login.

For users who wish to transfer their learning progress to another device, the app provides an optional Transfer feature. When you choose to back up your data, the app:

• Generates a random Transfer ID (e.g., XXXX-0000) that is not linked to your identity
• Uses anonymous authentication via Supabase to securely store the backup
• Stores only your learning progress (mastered words, streak, nickname) — no personal data

We do not collect your email address, Apple ID, Google account, phone number, or any device identifiers.

6. Third-Party Services

The App uses the following:

• Supabase – used only for the optional Transfer feature (anonymous data backup). Privacy policy: supabase.com/privacy
• Text-to-Speech (expo-speech) – uses your device's built-in TTS engine. No audio is sent to our servers.
• expo-notifications – schedules local reminders on your device. No notification data is sent to our servers.

We do not integrate any advertising networks or analytics SDKs (e.g., Firebase, Amplitude). We do not use email-based or social media authentication.

7. Children's Privacy

Japanese Sensei is designed for adult foreign workers. We do not knowingly collect any information from children under 13.

8. Data Deletion

Locally stored data: uninstall the App to remove all learning progress stored on your device.

Transfer backup data: backups created via the optional Transfer feature are automatically purged from our servers after 90 days of inactivity. To request immediate deletion of a specific Transfer ID, contact us at the email below.

9. Changes to This Policy

If we update this policy, the new version will be posted at this URL with an updated effective date.

10. Contact

Questions? Contact us at: katanaapps.dev@gmail.com