麻雀の書Mahjong Book

PRIVACY

Privacy policy

CLEAR EDITION, K.K. ("we") handles information in the Mahjong Book app and its official website as described below.

1. Lessons and offline games

Learning progress, settings such as language and volume, and saved offline games are stored on your device. Your learning history is not sent to the server to provide online games. Deleting the app or changing devices may result in losing locally stored data.

2. Online games

To run games, restore connections and prevent duplicate actions, we exchange and store the following information with servers provided by Cloudflare:

Your device stores your participant ID and reconnection information. The server stores a hash of the reconnection secret. IP addresses are also used to handle connections and limit abusive repeated requests. The country or region code is country-level information, not GPS location data.

Other players in the room can see your display name, country or region, seat, connection state, scores, discards, melds and other information needed to play. The public lobby shows rooms accepting players. Hidden hands and the tile wall order are not sent to other players' normal game views. Chat uses preset phrases; there is no free-text chat input.

3. Online retention and deletion

Room and game information is stored in Cloudflare Durable Objects while needed for play and reconnection. A room becomes eligible for deletion by the maintenance task after 20 minutes without an update. A disconnected participant record with no remaining room membership is deleted by the maintenance task after a 90-second grace period from the last action or disconnection. Records are not simply deleted after 90 seconds while a game or room membership continues.

Duplicate-action records are refreshed using up to 64 recent records per participant that are less than 30 minutes old. Maintenance normally runs at intervals of one minute or less, but an outage may delay it. We do not maintain a separate permanent database of every game played.

After deletion from active storage, information may remain in Cloudflare's recovery backups for up to 30 days. Operational logs, including request times, URLs, responses and error information, are retained in Cloudflare Workers Logs for up to seven days. Network information processed by Cloudflare itself for delivery and security is subject to its policy and contractual terms.

4. Contact form

The form collects your reply email address, enquiry category and message, plus your optional name, device and OS details, and app version. We use these to respond, investigate problems and handle requests about your data. Attachments are not supported. Do not include passwords, reconnection tokens or verification codes.

The form is designed to receive enquiries through Cloudflare Pages Functions and deliver them through Formspree to a Gmail inbox we manage. Cloudflare Turnstile checks for abusive submissions and processes information such as your IP address and browser details. The form does not automatically save its contents in browser storage.

We delete the enquiry records we hold within one year after the enquiry is resolved, unless a legal obligation or a specific dispute requires us to retain them for longer. In that case, we retain them only as long as needed for that purpose. Formspree's free plan stores 30 days of submission history in its dashboard. Logs needed for security and other purposes are retained under its policy. Our mailbox and the delivery provider's records are managed separately.

5. Service providers and international processing

We use Cloudflare, Inc. for website delivery, online game hosting, connection security and form processing; Formspree, Inc. for accepting enquiries and sending email notifications; and Google's Gmail to receive and store enquiry emails. These providers process information needed for their services under their terms and privacy policies. Cloudflare and Google process information globally, and Formspree hosts its services in the United States. Storage is not restricted to Japan.

Cloudflare privacy policy / Formspree privacy policy / Google privacy policy

Apple or Google processes app purchases and payments. Our contact form does not collect payment card details. Information handled by the stores is subject to their respective policies.

6. Advertising, analytics and sharing

This website does not include advertising cookies, analytics tags or third-party video players. Videos and fonts are served by this site. We do not sell the information we collect or share it for behavioural advertising. We do not provide personal information to third parties except for service provision on our behalf, with your consent, where required by law, or as otherwise permitted by applicable law.

7. Access, correction, deletion and other requests

For requests to access, correct, delete or restrict the use of information, select "Data and privacy" in our contact form. We may ask for relevant details, such as when you played, your display name or room code, to identify the information concerned. You do not need to send secrets such as reconnection tokens.

An anonymous participant ID alone may not allow us to identify you or the relevant data. We will act on what we can verify in accordance with applicable law. We cannot remotely delete information held only on your device. Uninstalling the app does not immediately erase online information; the deletion process described above still applies.

8. Operator and changes

Operator: CLEAR EDITION, K.K.
Contact: Contact form

We will provide our business address and representative information without delay upon request through the form. We update this page when our practices change, and communicate material changes through the app or this website.

Effective and last updated: 10 September 2026.