Legal

Privacy Policy

Last updated: July 2026

Mugi合同会社 ("Mugi," "we," "our," or "us") operates the Mugi app and the website at mugi-app.com (together, the "Service"). This Privacy Policy explains what information we collect, how we use it, and your rights regarding it.

By using our app or website, you agree to the practices described in this policy.

1. Information We Collect

Account information. When you create an account by email and password, we collect your email address and a securely hashed password. If you sign in with Apple or Google, we receive a unique identifier and, if you choose to share it, your name and email. We never receive your Apple or Google password.

Study progress and usage data. In-app activity such as quiz results, review/flashcard history, SRS scheduling data, study streaks, saved words, watch history, and feature usage. This powers your personalized review system and the app's learning features.

Subscription and purchase information. If you subscribe to Mugi Pro, our payment processor, RevenueCat, and the app store you purchased through (Apple App Store or Google Play) process your purchase and share subscription status (e.g., active, trial, expired) and an anonymized purchase identifier with us so we can grant access to paid features. We never see or store your credit card number or other payment credentials — those are handled entirely by Apple, Google, and their payment systems.

Device and diagnostic information. Basic technical data such as app version, operating system, and crash/error logs, used to keep the app working correctly.

2. How We Use Your Information

• To create, secure, and manage your account
• To personalize your study experience and track your learning progress
• To grant and manage access to paid subscription features
• To send you app-related updates and important announcements
• To improve the app based on aggregate usage patterns
• To respond to your support requests
• To detect, prevent, and address technical issues or misuse

We do not sell your personal information to third parties, and we do not use your study content (words looked up, videos watched) for advertising purposes.

3. How We Store Your Data

Your progress, saved words, and settings are stored locally on your device, and synced to our cloud database (hosted via Supabase) so your data is available if you sign in on another device. We take reasonable technical and organizational measures to protect this data from unauthorized access, loss, or misuse. No method of transmission or storage is completely secure, and we cannot guarantee absolute security.

4. Third-Party Services

We use the following third-party services, which may process data according to their own privacy policies:

5. YouTube Embedded Video Content

Some of Mugi's learning features play publicly available YouTube videos using YouTube's official embedded player. When a video loads,YouTube (Google) may set its own cookies and collect data about the video view directly — this happens on YouTube's side, independently of Mugi, and is governed by Google's own Privacy Policy (policies.google.com/privacy), not this one. We do not control what YouTube collects during embedded playback.

We do separately record, on our own systems, which videos you watched within Mugi (title and timestamp) as part of your study/watch history described in Section 1 — this is used only to power your progress tracking and is not shared with YouTube or used for advertising.

6. Data Retention

We retain your personal information for as long as your account is active or as needed to provide the Service. Subscription and purchase records may be retained longer as required for accounting, tax, or legal purposes. You may request deletion of your account and associated data at any time by contacting us.

7. Children's Privacy

Mugi is not directed to children under the age of 13 (or the minimum age of digital consent in your jurisdiction), and we do not knowingly collect personal information from children under that age. Mugi includes embedded, publicly available YouTube video content that is not curated or filtered for age-appropriateness, and is not intended for use by young children.

If you are a parent or guardian and believe your child has provided us with personal information, please contact us atcontact@mugi-app.com and we will promptly investigate and delete such information as appropriate.

Subscribing to Mugi Pro requires a payment method and should only be done by an adult. See Section 7a below.

7a. Payments

Purchases should be made by an adult, or by a minor with a parent or guardian's knowledge and permission. We rely on the app stores' own age-verification and parental consent controls (e.g., Apple's Ask to Buy, Google Play's parental supervision tools) for purchases; we do not independently verify a purchaser's age.

8. Your Rights

Depending on your location, you may have the right to:

• Access the personal information we hold about you
• Request correction of inaccurate information
• Request deletion of your personal information
• Withdraw consent at any time
• Request a copy of your data in a portable format

To exercise any of these rights, contact us at the email below. We will respond within a reasonable time as required by applicable law (including Japan's Act on the Protection of Personal Information, and, where applicable, GDPR or CCPA).

9. International Data Transfers

Mugi合同会社 is based in Japan; some of our service providers (e.g., Supabase, RevenueCat) may process or store data outside Japan. Where required by law, we take steps to ensure such transfers are subject to appropriate safeguards.

10. Changes to This Policy

We may update this Privacy Policy from time to time. When we do, we will update the "Last updated" date at the top of this page. We encourage you to review this policy periodically.

11. Contact

If you have any questions about this Privacy Policy, please contact us at:
contact@mugi-app.com

See also our Terms of Service.