Privacy Policy

This policy sets out how 4peiron (“the Service”) handles personal data.

Last updated: 11 August 2026

1. Who we are

Operator: KustomApe, inc.
Address: Yokohama, Kanagawa, Japan
Data protection officer: Eisuke Nakanishi

2. What we collect

The Service collects the following.

  • Your email address (for signing in, sending the newsletter and replying to enquiries).
  • Payment-related information (plan, subscription status, subscription ID). We never collect or hold credit card numbers. Card details are collected and held directly by our payment processor, Stripe, Inc.
  • Likes and view counts. These are recorded against your account when you are signed in, and against a value identifying your browser session when you are not. They exist so that the same person is not counted twice; they are not used to record what you have studied.
  • Access logs (IP address, user agent, timestamp, requested URL), kept for incident response and security.

3. What we use it for

  • Providing the Service, verifying who you are, and determining your plan
  • Billing and checking payment status
  • Answering enquiries and contacting you when needed
  • Sending announcements and the newsletter to subscribers
  • Preventing abuse, investigating incidents and improving the Service

4. Sharing with third parties

We do not pass personal data to third parties without your consent, except where the law requires it. We do, however, entrust processing to the following providers as far as running the Service requires.

5. How long we keep it

For as long as the purpose requires, and for any period the law mandates (up to seven years for transaction records, per the applicable statutes); after that we delete or anonymise it promptly. Access logs are deleted roughly 90 days after collection.

6. Cookies and similar

We use cookies to keep you signed in and to remember the language you read the site in; these are necessary to provide the Service. You can clear them at any time by signing out or through your browser settings.

We also use Google Analytics 4 to see which pages are read, and how much. Cookies set by Google record the pages viewed, the time spent and an approximate region; the results are aggregated in a form that does not identify you. We do not use any of it for advertising (Google signals and ad service integrations are switched off).

You can stop this at any time with Google’s opt-out add-on, or from your browser’s cookie settings. Nothing else about the Service changes if you do.

7. Security measures

All traffic is encrypted with TLS. Secrets such as payment API keys live only in server environment variables and never appear in code sent to the browser. Access to personal data is limited to staff who need it for their work.

8. Access, correction and deletion

On request from the person concerned, we will disclose, correct, suspend the use of, or delete the personal data we hold. Please contact us. Once we have verified your identity we aim to act within 3 business days.

9. Changes to this policy

We may revise this policy as the law or the Service changes. For significant changes we will tell you, either on this page or by email to your registered address.

10. How to reach us

For anything about how we handle personal data, write to kustomape@gmail.com.