Privacy Policy
Last updated: July 8, 2026
This is a complete English translation of cotobo’s Privacy Policy, provided for convenience. The
Japanese version is the governing text. In the event of any conflict or discrepancy between this translation and the Japanese original, the Japanese version controls.
cotobo is currently provided as a beta service. This Policy may be revised in the future; if it is, we will update this page to announce the change.
Tomoki Kawashima (“the Operator”) sets out this Privacy Policy (“this Policy”) for how personal information is handled within cotobo (“the Service”), a lesson-management service for teachers.
Article 1 (Information We Collect)
1. Teacher (user) account information
- Email address; password (managed within our authentication provider — the Operator never holds it in plain text); display name; time zone; default currency; and other in-app settings.
- If Google Calendar sync is set up: the email address of the connected Google account, an authentication token (stored encrypted), and event data from the calendars selected for sync (read-only — cotobo never writes events back to Google Calendar).
2. Student information entered by Teachers
- Name, email address, target/native language, interests, level, time zone, lesson schedule and fees, lesson notes and memos the Teacher records, portal access settings, and similar information.
- This information is entered by the Teacher for their own use of the Service — the Operator does not collect it directly from students.
3. Usage logs and similar data
- Log data such as access timestamps and IP addresses.
- Information stored in cookies and local storage (see Article 4 for details).
Article 2 (Purposes of Use)
- To provide the Service (lesson records, student management, fee and finance management, calendar sync, invoicing, the student portal, and the like).
- To provide AI-assisted features, such as generating example sentences, fill-in-the-blank exercises, katakana readings of student names, vocabulary-lookup assistance, and review quizzes.
- To send lesson-review reminder emails, invoice emails, and the like.
- To investigate and respond to issues, and to maintain and improve the Service.
Article 3 (Disclosure to Third Parties)
The Service uses the following third-party services, and shares the information necessary for each stated purpose:
| Recipient | Purpose | Information shared |
|---|
| Supabase | Database and authentication platform (where the Service’s data is stored) | All data within the Service — teacher account information, student information, lesson records, and more. |
| Vercel | Hosting and server runtime environment for the Service | Access logs, etc. |
| Google Calendar API | Only when a Teacher sets up Google Calendar sync, to read events from the selected calendars (read-only) | The connected Google account’s email address, and calendar event data. |
| Anthropic API (Claude) | Processing for AI features (example-sentence generation, fill-in-the-blank exercises, katakana readings of student names, vocabulary-lookup assistance, review-quiz generation) | Depending on the feature: material text, portions of lesson notes the Teacher has entered, and the student’s target language, level, and interests. Only the katakana-reading feature also sends the student’s name. |
| DeepL API | Translation of lesson notes and similar content | Only the text selected for translation. |
| Resend | Sending email (lesson-review reminders, spaced-repetition reminders, invoice delivery, availability notices) | The recipient’s email address, plus — depending on the email type — the student’s name, lesson content, invoice details, and similar information. |
| Exchange-rate API (exchangerate-api.com) | Retrieving exchange rates for currency conversion | None — only exchange-rate data, which contains no personal information. |
Beyond what is listed above, the Operator does not disclose personal information to third parties without the individual’s consent, except as required by law.
Article 4 (Cookies and Local Storage)
The Service uses cookies and browser local storage for the following purposes. They are not used for advertising or tracking.
Essential (required to provide the Service)
- Authentication session cookie (keeps you logged in)
- A temporary CSRF-protection cookie used during Google Calendar linking
- Student portal session cookie (keeps the portal login state)
Optional (to preserve your experience of the Service)
- Display preferences (sidebar open/closed state, notebook editor font size and line spacing, etc.)
- The language last selected in the translation feature
- The student portal’s display language setting
- Whether the “Getting Started” guide banner has been dismissed
Article 5 (Retention Period and Deletion)
- Collected information is retained for as long as a Teacher uses the Service, to the extent necessary to provide it.
- Teachers can delete their own account from Settings. Doing so permanently deletes all registered data — including student information, lesson records, notebooks, invoices, and material files — and it cannot be restored.
- Requests from a student for disclosure, correction, or deletion of their own information will be handled — either through the student’s Teacher, or by contacting us at the address in Article 7.
Article 6 (Teacher Responsibility for Student Information)
Student Information is entered into the Service by the Teacher. Explaining this to the student and obtaining their consent is the Teacher’s responsibility. See the Terms of Service for details.
Article 7 (Contact for Inquiries and Disclosure Requests)
For questions about this Policy, or requests to disclose, correct, or delete personal data we hold, please contact us at the address below.
cotobo@proton.me