Privacy Policy
Last updated: 2026-10-30
Effective date: 2026-10-30
Version: 1.0
If there is any inconsistency between the English and Japanese versions, the English version prevails.
1. Who we are
Naruhodo Sensei ("the Service", "the App") is a Japanese-language learning web application operated by:
ヤークス株式会社 (YARKS Inc., "we", "us", "our")
Representative: Sebastien Hebert
Address: 〒935-0011 富山県氷見市中央町9番47号 (9-47 Chūō-chō, Himi City, Toyama 935-0011, Japan)
Contact for privacy matters: support@yarks.jp
We are the business responsible for your personal information under Japan's Act on the Protection of Personal Information (APPI). Because we also offer the Service to users in the United States, this policy includes a section on U.S. state privacy rights (§11).
The Service is not offered to, or directed at, residents of the European Union, European Economic Area, United Kingdom, or Switzerland.
2. The information we collect
We collect only what the Service needs to work. We do not use advertising, analytics, crash-reporting, or tracking SDKs, and the App contains no third-party advertising or marketing trackers.
a. Account and sign-in
- Email address, and authentication details managed by our authentication provider.
- If you sign in with Google ("Google Sign-In"), we receive the basic account identifiers Google returns for sign-in. We do not post to your Google account.
- A user ID we assign to your account.
b. Age confirmation
- When you first use the Service you confirm your age by entering your birth year and month only. We store a derived age indicator and the time you confirmed it. We do not store your full date of birth.
c. Learning activity
- Your study progress: review/spaced-repetition history, practice-drill results, reading/listening comprehension progress, levels, and your daily streak.
- Limited quality telemetry tied to your account (e.g. which answer options you chose, question reports) used to improve lesson content.
d. Content you create while using AI features
- AI tutor chat ("Sensei"): the text you type to the AI tutor, and the tutor's replies.
- Speaking practice: a text transcript of what you say and of the AI's replies, plus correction notes. We do not store the raw audio of your voice (see §4).
- Support messages: anything you write to us through the support flow.
The Service has no notes, custom decks, user profiles, or any feature to post or share content publicly or with other users.
e. Payment information
- When you purchase a subscription or credits, we store transaction records (our internal customer identifier, purchase amounts, credit ledger entries, coupon use). Your card details are entered on our payment provider's hosted checkout and never pass through or get stored by us.
f. Device permissions
- Microphone: requested by your browser only when you use speaking practice (push-to-talk). Audio is used live and discarded (see §4). No other device permission (camera, location, notifications) is requested.
g. Information stored locally in your browser
We store a small number of items in your browser's local storage to make the App work. These are not advertising or tracking cookies:
| Item | Purpose |
|---|---|
| Consent choice + category selections + an anonymous identifier | Remember your cookie/SDK consent choice |
| Theme setting | Remember light/dark/system theme |
| Language setting | Remember your chosen language |
| Onboarding level | Carry your chosen starting level through sign-up |
| Chat resume target | Return you to where you left off in the AI tutor |
h. Technical/connection data
Because the App is served over the internet, our hosting/CDN provider processes standard request metadata including your IP address, which is also used for a region-availability check. Our font provider receives your IP address when fonts are loaded (see §5).
3. Why we use your information, and our legal basis
| Purpose | Legal basis (APPI / general) |
|---|---|
| Create and operate your account; authenticate you | Performance of our contract with you |
| Deliver lessons, track learning progress, run spaced repetition | Performance of our contract |
| Provide AI tutoring and speaking practice | Performance of our contract |
| Process subscriptions, credits, and payments | Performance of our contract; legal obligation (accounting/tax) |
| Confirm you are 18 or over | Legal obligation; our legitimate interest in age-appropriate service |
| Check region availability | Our legitimate interest in offering the Service only where intended |
| Improve content quality (telemetry, question reports) | Our legitimate interest in improving the Service |
| Respond to support requests | Performance of our contract; our legitimate interest |
| Keep security and audit records | Legal obligation; our legitimate interest in security |
We do not sell your personal information, and we do not use your personal information for advertising or for building advertising profiles.
4. AI and voice features — what is sent where
The Service uses third-party AI providers to deliver two features. Your learning content is sent to them only to produce your result, and not to train their models (we use no-training service tiers — see §6):
- AI tutor (text): when you chat with the Sensei tutor, the text of your question and the relevant lesson context are sent to Anthropic (Claude) to generate a reply. We do not send your name or email with these requests.
- Speaking practice (voice): when you speak, your browser streams the audio directly to Google (Gemini Live) for live transcription and conversation. This audio is processed in real time to produce text and the AI's spoken reply; we do not record or store the raw audio, and no voiceprint, speaker-identification signature, or other biometric template is ever created or stored. Only the resulting text transcript and correction notes are saved to your account. Voice is used solely for transcription and scoring, never to identify you.
AI-generated explanations and corrections may contain errors and are for learning only (see the Terms of Service).
5. Service providers and international data transfers
We use the following providers ("subprocessors") to run the Service. Several are located outside Japan, which means your personal information is transferred and processed overseas. Under APPI we disclose the recipients and the countries below.
| Provider | What they receive | Purpose | Country |
|---|---|---|---|
| Supabase | All stored account data, including your email | Database, authentication, file storage, server functions | Singapore |
| Anthropic (Claude) | AI-tutor prompt text and lesson context (no name/email) | AI tutoring | United States |
| Google (Gemini Live) | Live speaking audio (not stored by us) | Real-time speaking practice | United States / global |
| Stripe | Payment identifiers and amounts (not card data, which you enter directly with Stripe) | Payments, subscriptions | United States / Ireland |
| Cloudflare | Request metadata including IP address | Hosting/CDN; region-availability check | Global edge network |
| Google Fonts | Your IP address (when fonts load) | Display the App's fonts | United States / global |
We require these providers, by contract, to protect your information and to process it only to provide their service to us.
All stored personal data physically resides in Singapore (our database region). AI, payment, and font providers additionally process data in the United States.
6. How long we keep your information
| Data | Retention |
|---|---|
| Account, learning activity, AI chat/transcripts, support messages | For the life of your account; erased when you delete your account |
| Purchased credits | Do not expire (they remain in your account until used or until you delete your account) |
| Transaction / payment records | On account deletion, personal details are removed but the transaction records are kept in anonymized form (no longer linked to you) as required for accounting and tax obligations |
| Security / audit logs | At least 1 year |
| Local browser storage | Until you clear it in your browser |
7. Your rights
You can exercise the following rights at any time:
- Access / export: download a copy of your data in the App, under Profile → Data & privacy (returns a machine-readable JSON copy of your account data).
- Deletion: delete your account and personal data in the App, under Profile → Data & privacy. Deletion takes effect immediately and removes your personal data (subject to the anonymized transaction-record retention in §6).
- Correction: update your account details in the App, or contact us.
- Suspension of use / objection: contact us at support@yarks.jp.
To make any request, or if you have questions, email support@yarks.jp. We may need to verify your identity before acting on a request.
8. How we protect your information
Security measures actually in place:
- Each user's data is isolated at the database level (row-level security), so one account cannot read another's data.
- Data is encrypted in transit (HTTPS/TLS) and encrypted at rest by our database provider.
- Card details are never handled or stored by us — they go directly to our payment provider.
- Raw voice audio is never stored, and no biometric/voiceprint data is created.
- Administrative access is restricted, and sensitive administrative actions are recorded in an audit log.
No method of transmission or storage is 100% secure, but we work to protect your information using appropriate measures.
9. Children
The Service is for users aged 18 and over. It is not directed to children, and we do not knowingly collect personal information from anyone under 18. We confirm age at first use. If we learn that we have collected information from someone under 18, we will delete it.
10. Cookies and local storage
The App does not use advertising or cross-site tracking cookies. It stores the small set of functional items listed in §2(g) in your browser's local storage. A consent banner lets you choose whether to allow any non-essential categories; today no non-essential (analytics/marketing) technologies are active, and none will be enabled without your consent.
11. United States — your state privacy rights
If you are a U.S. resident (for example, in California under the CCPA/CPRA, or in other states with comprehensive privacy laws), the following applies:
- Categories of personal information we collect: identifiers (email, user ID, IP address), account and commercial information (subscription/credit/purchase records), internet activity related to your use of the App (learning progress), audio/voice processed in real time but not stored, and the content you provide to the AI tutor and support.
- We do not "sell" your personal information, and we do not "share" it for cross-context behavioral advertising. We have no advertising or ad-tracking SDKs.
- Your rights: to know/access, delete, and correct your personal information, and to not be discriminated against for exercising these rights. Use the in-App tools (§7) or email support@yarks.jp.
- We do not use your personal information for automated decisions that produce legal or similarly significant effects.
12. Contact and complaints
For any privacy question or request: support@yarks.jp.
Postal: ヤークス株式会社, 〒935-0011 富山県氷見市中央町9番47号.
Phone: provided to users without delay on request (email support@yarks.jp). Support is by email; we aim to reply within 3 business days.
In Japan, you may also contact the Personal Information Protection Commission (PPC) if you believe your information has been handled improperly.
13. Changes to this policy
We may update this policy. If we make a material change, we will update the effective date above and, where appropriate, notify you in the App. Your continued use after a change means you accept the updated policy.