Privacy Policy

Established: August 29, 2026

This page is a reference translation. In case of any discrepancy, the Japanese version prevails.

S2 Co., Ltd. (the operator of mind masters; "we/us") handles user information in the mind-mapping app "mind masters" ("Service") as follows.

1. Information We Collect

LINE account information: Through LINE Login we obtain your user identifier (LINE user ID), display name, and profile image URL.
Map data: The content of mind maps you create is stored on our servers only in a form encrypted on your device. We do not hold the decryption keys and cannot view your maps. The content of shared maps and members' display names are likewise encrypted so that only participants who know the invite link can decrypt them.
Usage data: To improve the Service, we record a random anonymous ID per device and operation events (e.g. login, map creation, sharing). This record contains no map content, names, or LINE user IDs.
Cookies etc.: Settings needed for operation (such as language) are stored in your browser's localStorage. We use no advertising cookies.
Analytics (Google Analytics): Only on the template introduction pages (under /t/) and the pre-login introduction page, we use Google Analytics (Google LLC) to understand traffic. Information such as pages viewed and browser data is sent to Google via cookies, but nothing personally identifying is included. It is not used inside the app after login. See Google's policy for details; you can opt out with the Google Analytics Opt-out Add-on.

2. Purposes of Use

Providing the Service (cross-device sync, co-editing, authentication)
Improving quality, fixing issues, analyzing usage
Delivering important notices (via the LINE official account, etc.)

3. Third Parties and Processors

Except as required by law, we do not provide user information to third parties. We use the following providers to run the Service.

Vercel Inc. (USA) — server hosting and data storage (encrypted data only)
LY Corporation — authentication via LINE Login and LINE platform features
Google LLC (USA) — access analytics (Google Analytics; template introduction pages and the pre-login page only)
Stripe, Inc. (USA) — payment processing for paid plans. Card details are handled directly by Stripe and never stored on our servers; we keep only a customer identifier and subscription status.

4. Retention and Deletion

Map data is deleted from our servers when you delete it in the app (deletion records used to sync deletions across devices are kept for up to 90 days).
To request deletion of all data tied to your account, contact us below.

5. Security

All communication is encrypted with TLS, and map data is stored encrypted with AES-256 performed on your device. Access to our servers requires authentication by the LINE platform.

6. Chrome Extension

Our Chrome extension shows the Service in a side panel next to the page you are viewing. It handles data as follows.

Selected-text import: Only when you run the import from the right-click menu, the selected text and page title are stored temporarily in the browser (the extension's local storage) and handed to the Service inside the side panel. The temporary copy is deleted once handed over, or after 10 minutes, and is never sent anywhere other than the Service.
LINE Login: When you sign in from the side panel, the LINE Login authorization code is sent to our server to be exchanged for an access token. The token is stored only in your browser.
Not collected: The extension does not collect or transmit your browsing history, page content (other than text you explicitly import), or cookies.
We never sell or transfer data obtained by the extension to third parties, nor use it for advertising or creditworthiness purposes (we comply with the Limited Use requirements of the Chrome Web Store User Data Policy).

7. Changes to This Policy

We may update this Policy as needed. For material changes, we will notify you on the Service.

8. Contact

For inquiries about this Policy, please message the mind masters LINE official account.