This English version is a reference translation. The Japanese version is the governing text; if the two differ, the Japanese version prevails.
This Privacy Policy explains how user information is handled in the smartphone app "One Lyric" (the "App") provided by the sole proprietor "15C" (the "Developer"). AI diary analysis, song search and related features are available once you agree to this policy and the Terms of Service.
The App handles the following information that you enter or select in the App. Diary text and photos stay only on your device unless you run "Find a song for this memory" or "Generate image"; otherwise they are never sent to the Developer's server.
| Item | Description | Where it is stored |
|---|---|---|
| Diary title and text | Text you enter. It may include sensitive matters such as your physical or mental condition or worries. | On device (always) Server (when you search, generate an image, or save) |
| Photos | Images you take with the camera or choose from your gallery. Photos attached to a saved entry are copied into the App's private storage. | On device (always) Server (when you search using the photo) |
| Song suggestions | Song titles, artist names, links, etc. suggested by the Developer's server based on AI analysis of your diary and photo. The song you choose is saved with the entry. | On device Server (when you save) |
| AI-generated images (Premium) | Illustrations generated by AI from your diary when a Premium member runs "Generate image". | Not stored on the server (only shown to you), except images you report |
| Reports of AI-generated images (optional) | If you report a generated image with "Report" in the App: the image (downscaled), the reason and any comment you add. Used only to review inappropriate output and prevent it recurring, and deleted when you delete your account. | Server |
| Anonymous ID | A random ID assigned per device instead of a login (Firebase UID). It contains no information that directly identifies you, such as your name or email address. | On device Server (sent with requests) |
| Email address (optional, only if you set up sign-in) | Obtained only if you set up sign-in with a Google account or email address, so you can keep your diary and Premium status after changing devices or reinstalling. Passwords for email sign-in are managed by Firebase (Google); the Developer does not hold them. | Firebase (Google) Server (as part of authentication) |
| Consent records | When and to which version of this policy and the Terms you agreed, and your self-declared age (18 or older / 13–17 with a parent's or guardian's consent). | Server |
| Created/updated times | When each diary entry was recorded. | On device Server (when you save) |
| Premium purchase status | Purchase, renewal and cancellation status of Premium, managed through RevenueCat and linked to your anonymous ID (or the ID of your signed-in account). It does not include payment details. | Google Play / RevenueCat Server (when checked) |
| Ad views and rewards (optional, free members only) | Records that a rewarded ad was shown and watched to completion, and of the rewards granted (an extra search, one use of "Search from Text and Image"): date granted, expiry and usage. Linked to your anonymous ID. | Google AdMob / RevenueCat Server (to grant and check rewards) |
| Ad display and revenue information (free members only) | Ad loading and display, ad type and placement, estimated revenue per ad, etc. To serve ads, information defined by Google AdMob, such as the device advertising ID and approximate location, may be used. | Google AdMob / RevenueCat |
| Crash and error information | Stack traces when the App crashes, and technical information such as device model, OS version and app version needed to investigate bugs. Linked to your anonymous ID. | Firebase Crashlytics (Google LLC) |
| Access logs | IP address, request time, etc. (to detect abuse and enforce usage limits). | Server |
You can use the App without signing in. The App does not collect your name or location, and obtains an email address only if you choose to set up sign-in. Sensitive information that diary text and photos may contain is obtained only through your own input or selection, never from third parties or by other means. By agreeing to this policy, you consent to that collection. See section 3 for when data is sent to the server.
Used only when you choose "Take Photo" to attach a photo to a diary entry. Photos you take or select are normally stored only on your device, but if you run "Find a song for this memory" with a photo attached, it is sent to the Developer's server as described below.
The App communicates with the Developer's server (hosted on Cloud Run on Google Cloud) to suggest songs that match your diary. When you run the search, the following information is sent:
What is sent is used only to analyze the diary and photo (using AI) and to search for matching songs. Nothing is sent unless you run the search. Weekly and monthly theme-song searches combine, on the server, the analyses of diary entries you have already saved.
When a Premium member runs "Generate image", the diary text at that moment is sent to the Developer's server and to an AI image service (see section 5 for the provider) to generate an illustration. The generated image is only shown to you and is never stored on the Developer's server. However, if you report a generated image as inappropriate with "Report" in the App, that image and your report are stored on the server for review.
Free members can receive the following rewards by watching a rewarded ad served by Google AdMob to the end. Watching ads is entirely optional.
Daily counts reset at midnight Japan Standard Time (UTC+9). Before ads are shown, users in the European Economic Area (EEA), the UK and Switzerland are asked for consent through Google's consent form (User Messaging Platform). You can change your choices at any time from "Privacy options" in the App's account settings. Users who declare they are under 18 are shown only non-personalized ads.
Diary data and photos are stored in the App's private storage on your device. The Developer cannot view data on your device.
When you use the song search, the diary text at that moment (and the photo, if attached) is sent to the Developer's server and used to generate suggestions. When you save an entry, its content is recorded on the server together with the chosen song, and kept to provide and improve the suggestion feature. Diary text sent for "Generate image" is used only for generation and is not stored on the server.
Diary data recorded on the server (text, images and suggestion history) is deleted automatically if the App is not used for 2 years after your last sign-in. You can also delete all your diary data on the device and on the server at any time from "Delete all data" in the App's account settings.
Android's built-in feature may automatically back up app data to your own Google account. This is an OS feature and the Developer does not receive its contents. You can turn it off at any time in your device's Settings (e.g. System > Backup).
The Developer never sells user information. The App contains no analytics SDK that tracks your behavior and shares it with advertisers. To provide the App's features, information is sent to the following providers. Diary text and photos are sent only to the providers listed for them below.
| Provider | Information sent | Purpose | Country |
|---|---|---|---|
| OpenAI, L.L.C. | Diary text, diary photos, candidate song information | Emotion analysis, ranking songs, AI image generation (Premium) | United States |
| Musixmatch Ltd. | Search keywords extracted from the diary, titles and artists of songs in the results | Song search, fetching lyric snippets | United Kingdom |
| Google LLC (Firebase Authentication, App Check, Cloud Storage, Cloud Run) | Anonymous ID, email address if you set up sign-in, app integrity information, diary photos | Authentication, preventing automated abuse, storing diary photos, running the server | United States and other countries (Google data centers) |
| Google LLC (AdMob) | Information needed to serve ads, such as the device advertising ID and approximate location; reward verification data including your anonymous ID | Serving rewarded ads and verifying completion for rewards (free members only) | United States and other countries (Google data centers) |
| Google LLC (Firebase Crashlytics) | Crash and error information, anonymous ID | Finding and fixing bugs | United States and other countries (Google data centers) |
| RevenueCat, Inc. | Anonymous ID, purchase and subscription status, rewarded-ad display, viewing and estimated revenue information | Managing Premium, measuring ads, verifying the "Search from Text and Image" reward | United States |
Links to Spotify in the search results are static links assembled from information Musixmatch already has; no information is sent to Spotify. Lyrics are shown only in part (near the beginning), within the scope of the Developer's license agreement with Musixmatch. Under OpenAI's API terms, data sent through the API is not used to train its models by default (as of OpenAI's policy in August 2026).
All of the providers above are located outside Japan, so sending data to them is a "provision to a third party in a foreign country" under Japan's Act on the Protection of Personal Information. By agreeing to this policy, you consent to such provision within the scope and purposes above (Article 28 of that Act). An overview of the destination countries' systems:
See the next section for Premium (in-app purchases).
The App offers a paid "Premium" subscription (auto-renewing) that unlocks features such as AI image generation. Payments are processed through Google Play billing, and the Developer never obtains or stores payment details such as credit card numbers.
Subscription status (purchase, renewal, cancellation) is managed with RevenueCat, Inc. Purchase and subscription information linked to your anonymous ID (or the corresponding ID of your signed-in account) is sent to RevenueCat, and the Developer checks your Premium status through RevenueCat. Payment details themselves are never passed to RevenueCat or the Developer.
Cancellations and refunds follow Google Play's terms and the conditions shown at purchase. You can cancel at any time from Subscriptions in Google Play (also reachable from the App's account settings) and keep using Premium for the period already paid for. Google Play's refund policy applies to refunds.
The App is not available to anyone under 13. Users aged 13 to 17 must obtain the consent of a parent or guardian. When giving consent, you are asked to self-declare your age and whether a parent or guardian has consented.
This policy may change due to changes in law or new features. For material changes, we will update the last-updated date and version and ask you to agree again in the App.
For questions or comments about this policy or how the App handles information, or to request deletion of your account or data, please contact us below. The operator's name, address and phone number are disclosed without delay on request.
If you live in the European Economic Area (EEA), the UK or Switzerland, the following applies in addition to the rest of this policy, under the EU General Data Protection Regulation (GDPR), the UK GDPR and the Swiss Federal Act on Data Protection.