Privacy policy

Last updated 14 November 2026 · what we actually store, in plain English

Mainichigo is an independent study service run by a small operator; it is not affiliated with any examination body or textbook publisher. This page describes what the service records about you and why.

What we collect

• Account: your username and email address, and your password — stored only as a salted hash, never readable by us. Email is required so we can verify the account and you can recover it.
• Learning data: your level, review history, quiz and exam results, lesson position and daily pace — the course cannot schedule your reviews without them.
• Tutor conversations: your text chat messages are stored with your account so the tutor can keep context between sessions. Scenario exercises are stored on our server with your sign-in session and removed when you sign out or the session expires. Voice conversations are not stored: we save neither the audio nor the captions, only a count of how much AI processing the session used.
• Security and operations: for each signed-in visit we record the IP address, time and browser (user-agent). The operator can see this to spot shared or hijacked accounts and to keep the service running. These records stay on our own server; they are not sent to any external lookup service. We also record how much AI processing each account uses (call counts, token counts and their cost) to manage the preview budget and spot abuse.

How it is used

To run the course, to secure accounts, to answer your messages, and — if the free preview ends — to email you about the service reopening. We do not sell your data and we show no advertising.

AI processing

The tutor's replies are generated by Google's Gemini API. Your messages and voice utterances — together with your current study level, lesson, recent weak points and studied vocabulary, which the tutor needs for context — are sent to Google LLC, a company located in the United States, for processing. The United States has no general data-protection law equivalent to Japan's; Google processes this data as our processor under its data processing terms, which commit it to confidentiality and security measures. We run the service on Google's paid enterprise tier, under whose terms your inputs are not used to train its models. By using the tutor you consent to this transfer. Please do not put sensitive personal information into tutor conversations.

Cookies and page assets

The site sets only the cookies it needs to work: a session cookie that keeps you signed in and a CSRF cookie that protects forms. There are no advertising or analytics trackers. Fonts, styling and scripts are served directly from this site's own server (first-party), so loading a page sends no request to any third-party content network.

Retention and deletion

Your data is kept while your account exists. Email us to delete your account and its data; deleted data may persist in routine backups for a limited time before those rotate out.

Your rights

You can ask us to show you the data we hold about you, correct it, stop using it, or delete it — email the address below and we will respond within a reasonable period.

Contact

Questions, disclosure, corrections or deletion requests: mainichigo.courses@gmail.com. To report a copyright concern, see the terms.