Tsuyoshi Chujo ("we" or "us") handles user information in the application "How Math Works" (the "App") as follows.

1. Basic Policy

The App does not collect personal information about its users in the course of using the experiences themselves. However, only when you use the subscription (paid) feature, we handle information to the extent necessary to process the purchase and confirm its status. Even then, we do not collect your name, email address, location data, or device identifiers.

2. Information Collection and External Transmission

  1. The App does not collect personal information such as names, email addresses, location data, or device identifiers.
  2. The App does not communicate over the internet in the experience part. Internet communication occurs only to process purchases and confirm their status for the subscription (paid) feature, and to display the external pages described in item 4 below. This communication is kept to the minimum necessary, and no information about how you use the experiences is transmitted.
  3. The information handled by the paid feature is your purchase history and an anonymous user identifier. This identifier is not linked to your name or email address and is used only to manage your purchase status.
  4. Documents such as the Terms of Service and this Privacy Policy, as well as the contact form, are provided as pages on external services (Notion and Google Forms) and displayed in an in-app browser. When you view or submit these pages, access information such as your IP address is sent to the providers of those services (Notion Labs, Inc. and Google LLC) and handled under their own terms and privacy policies. We do not collect user information through the display of these pages. Information you enter in the contact form is used only to respond to your inquiry.
  5. We use no external services or SDKs for analytics or advertising.
  6. The App has no account registration and never asks you to enter your name or email address to use the App.

3. Information Stored on Your Device

The App stores its settings (theme, display language, ordering of the experience list, control-panel position, and tutorial completion status) and a cache of your subscription unlock status only on your device. This information is never transmitted outside the device and is deleted when you uninstall the App.

Drawings made with the in-app memo feature are not saved and are erased when the screen is closed.

4. Provision to Third Parties

To provide the subscription (paid) feature, the App exchanges purchase-related information with the following third parties. This is limited to what is necessary for payment processing and purchase-status management; we do not provide user information to third parties for any other purpose.

  1. Apple Inc.: for payment processing through the app stores.
  2. RevenueCat, Inc. (United States): a data processor that manages purchase status. Your purchase history and anonymous user identifier are processed through this company.

Because processing through RevenueCat, Inc. takes place in the United States, purchase-related information is processed outside Japan (in the United States).

5. Information Handled by Platforms

App Store and the device operating system may collect statistical or other information under their own terms. This is outside our control; please refer to each platform's privacy policy.