Fusen

Privacy policy

Effective date: [DATE]

Fusen is made by an individual developer in Japan (“we”, “us”). This policy explains what information the Fusen app for Android, its desktop companion app and the Fusen account service collect, why, and what you can do about it.

Questions or requests: [SUPPORT EMAIL].

The short version

• Your notebook (saved words, sentences, notes, collections, and images saved with words) stays on your device. If you turn on sync, it goes to a hidden folder in your own Google Drive; images go there only if you also turn on Sync images. We never receive it.
• The dictionary is downloaded once and searched on your device. Looking up a word sends nothing anywhere.
• If you sign in to an account, we store your email address, your credits and records of how many credits each request used. We do not store the text you translate.
• When you use Fusen AI, the passage you translate or explain, or the image you ask it to read text from, is sent to our server and to the AI provider named below, used to answer you, and not kept by us.
• The app sends anonymous daily usage counts with no identifier and no text. You can turn this off.
• We do not sell your information, show ads or use your information for advertising.

Information that stays on your device

The following is stored only on your device and never sent to us:

• Your notebook: saved words, the sentences and translations saved with them, notes and collections.
• Images saved with words (a page you read text from, or a photo or screenshot you added). Android’s own backup to Google leaves them out; notebook backups include them, and sync sends them to your Google Drive only if you turn on Sync images (see below). Asking Fusen AI to read the text in an image sends that image once, as described under When you use Fusen AI.
• The dictionary and its index.
• Your settings.
• API keys you enter for DeepL, Anthropic or an OpenAI-compatible server, and your account’s session token. These are encrypted on the phone and left out of Android’s backups and of notebook backups.

Notebook backups you export, with the images saved with your words, are files you control. We do not receive them.

Information we collect

When you sign in to an account

Signing in is optional. You need an account only for Fusen AI: translation, explanations and reading text from images. You can sign in with Google or, where the app offers it, with an email address.

• Account: your email address (from Google, or the address you entered), your Google account ID if you signed in with Google, when the account was created and last used, and its status.
• Sign-in sessions: for each signed-in device, a session record with the device’s name (on Android, the phone model), its platform, and when the session was created and last used. A session that is not used for 180 days expires.
• Credits: your free and paid credit balances and the credits used this month.
• Usage records: for each AI request, the time, the kind of request (translation, explanation or text recognition), the model, the target language, the kind of text (for example a novel), the length of the text, the amount of AI processing used, its cost, the credits charged, whether the AI declined the text, and the app version. For text recognition, also the image’s size (in bytes and in pixels), the length of the text read, the number of speech bubbles found, and whether text was found where you tapped. The text and the image themselves are not recorded. We use these records for billing, support, preventing abuse and setting prices.
• Email sign-in: to send you a sign-in code, we store your address and a hashed copy of the code until it expires. Our email service (Amazon SES) keeps addresses that bounced or reported our mail as spam on its suppression list. To stop the sign-in from being used to send spam, we count requests per network using a hashed form of your IP address that changes every day and is deleted after 2 days. We do not store your IP address.

When you use Fusen AI

When you translate a passage or ask for an explanation with Fusen AI, the app sends our server:

• the passage (at most 2,000 characters);
• for context, up to five passages you looked up just before it in the same collection;
• for explanations, the word, its reading and the dictionary’s meanings for it;
• the target language and the kind of text (the collection’s kind, for example “novel”).

When you ask Fusen AI to read the text in an image (for example a manga page, a screenshot or a photo), the app sends our server:

• the page or screen you chose, as a JPEG image;
• where on it you tapped.

This happens only when you ask for it, and only while you are signed in to a Fusen account. Our server draws a ring where you tapped on a copy of the image, so that the AI knows which text you mean, and sends that copy to the AI provider. The copy carries none of the image’s metadata (such as where a photo was taken).

Our server sends this to the AI provider, returns the answer to you, and does not store the text or the image. Our server logs record the request (time, route, result, processing used and cost, and for an image its size) but never the text or the image. Logs are kept for 30 days.

AI provider: Anthropic, PBC (United States), through its API. Anthropic does not use data sent through its API to train its models, and keeps it only for a limited time, longer if it is flagged under Anthropic’s usage policies. See Anthropic’s privacy policy.

Do not send text or images you would not want processed by the AI provider. A screenshot shows everything that was on the screen, such as notifications and the time. Choosing a different translation engine, or turning off Translate by default, means nothing is sent until you tap the translate button.

Anonymous usage statistics

The Android app sends our server a summary of how it was used once a day, so that we can decide what to improve. The summary contains:

• counts of your actions on each day: lookups and where they came from (the reading app, as one of a fixed list of apps or “other”), dictionary hits and misses, translations by engine, words saved, edited and deleted, how quickly the popup opened, which features were used, and crashes;
• the size of your notebook, in ranges;
• a few settings: translation language and engine, gloss language, search scope, sort order and theme;
• whether a dictionary is installed and whether the account and sync are signed in;
• your device’s region setting, the app’s language, the app version and how long the app has been installed (in ranges).

It contains no words or text from your notebook or your reading, no account and no identifier. Our server adds it to totals and does not keep the summary itself. The server looks up which country your IP address is in and then discards the address. IP geolocation by DB-IP, licensed under CC BY 4.0.

Turn it off in Settings → Account and sync → Share anonymous usage statistics.

Feedback

If you use Send feedback, your email app opens a draft that includes the app version, the Android version, the phone model and the app’s language. We receive what you send, including your email address, and use it only to answer you.

Services you connect to yourself

These services receive information directly from your device. We do not receive it, and their own privacy policies apply.

• Google Drive sync. If you turn on sync, the app saves your notebook to the app-data folder of your own Google Drive, which only Fusen can see. It asks only for access to that folder (drive.appdata), not to the rest of your Drive. Images saved with words go there too only if you turn on Sync images (off by default, set on each device); they use your own Drive storage. We do not have a copy.
• Google sign-in. Google’s sign-in tells the app your email address and gives our server a token that proves which Google account you are. We do not receive your Google password.
• DeepL, Anthropic or an OpenAI-compatible server, if you choose one as the translation engine with your own API key: the passage you translate is sent directly to that service under your agreement with it. A server you enter yourself may use plain http, which is not encrypted.
• Google Translate. If you tap the Google Translate button, the passage is handed to the Google Translate app.
• Dictionary download. The dictionary (JMdict) is downloaded from the Electronic Dictionary Research and Development Group’s server (edrdg.org), which, like any website, sees your IP address.
• Google Play. If you installed the app from Google Play, Google may share crash reports and app statistics with us through Play Console, under Google’s privacy policy.

Google user data

Fusen’s use and transfer of information received from Google APIs adheres to the Google API Services User Data Policy, including the Limited Use requirements. We use Google user data only to provide sync and sign-in. We do not use it for advertising, do not sell it, and do not use it to train AI models.

Where your information is processed

Our server and its database run on Amazon Web Services in Tokyo, Japan. Text and images sent to Fusen AI are processed by Anthropic in the United States. The United States has no single national data-protection law like Japan’s Act on the Protection of Personal Information; personal information is protected there by sector-specific federal laws and by state laws such as California’s Consumer Privacy Act. Anthropic receives only the text and images described above, not your account or email address. Services you connect to yourself process your information where they operate.

How long we keep information

Information	Kept
Account, credits, sessions	Until you delete your account. Sessions expire after 180 days unused.
Usage records	400 days, or until you delete your account
Server logs	30 days
Email sign-in codes	Until they expire (15 minutes)
Hashed IP addresses for email sign-in	2 days
Anonymous usage statistics	Added to totals, which are kept
Text you translate or explain	Not kept by us
Images you ask Fusen AI to read text from	Not kept by us

After you delete your account, we keep a small record for 35 days (a year if the account was blocked for abuse), so that deleting and recreating an account cannot be used to get extra free credits. It holds your Google account ID or a hash of your email address, the free credits left that month, the number of requests the AI declined, and whether the account was blocked. It contains no email address in readable form and no usage records.

Your choices and rights

• Delete your account: in the app, Settings → Account and sync → Delete account, or without the app as described on our account deletion page.
• Turn off usage statistics: Settings → Account and sync → Share anonymous usage statistics.
• Delete synced data: Settings → Account and sync → Delete synced data deletes the notebook files and images sync keeps in your Google Drive.
• Remove Google access: in your Google account, Security → Third-party apps & services.
• Access, correction and deletion: you can ask us what we hold about you, and to correct or delete it, by emailing [SUPPORT EMAIL] from your account’s address. We answer within 30 days. Depending on where you live (for example under Japan’s Act on the Protection of Personal Information or the EU’s GDPR), you may have further rights, including to complain to your data-protection authority.

Security

All connections to our server use HTTPS. Session tokens are stored on our server only as hashes. Access to the server and database is limited to the developer, with multi-factor authentication.

Children

Fusen is not directed at children under 13, and we do not knowingly collect information from them. If you believe a child has created an account, contact us and we will delete it.

Changes

If we change this policy, we will update the effective date above. If a change affects what we collect or share, we will also say so in the app before it applies.

Contact

[SUPPORT EMAIL]

The developer’s name and address are provided without delay on request, as Japan’s Act on the Protection of Personal Information allows.