Privacy Policy

What we collect

• Account details. Your email address and password (stored as a hash by our sign-in provider). If you sign in with Google, we receive your email address and the basic profile details Google shares, such as your name.
• Learning settings. Your starting level, reading preference, lesson email time, and time zone.
• Learning activity. Lessons you open and complete, practice answers, review history, words you save, and your progress and streaks.
• AI Sensei conversations. The messages you send to AI Sensei, its replies, the lesson they belong to, and usage counts we use for fair-use limits.
• Payments. If you subscribe, Stripe processes your payment. We receive your subscription status and a Stripe customer reference. We never see or store your full card number.
• Email delivery. Whether a lesson email bounced, failed, or was marked as spam, so we can stop sending to addresses that don’t work.
• Usage analytics. Anonymous page views and a few product events (such as sign-up or lesson viewed) through Vercel Web Analytics, which does not use cookies.
• Technical data. IP address and browser details in server logs, kept by our hosting provider for security and debugging.

How we use it

We use this information to run your account, send your daily lesson emails, save your progress, schedule your reviews, answer your AI Sensei questions, manage your subscription, prevent abuse, and improve NihonFlow. We do not sell personal information, and we do not use it for advertising.

Who processes it

We rely on these service providers. Each one only receives what it needs to do its job.

• Supabase — database and sign-in. Data is stored in the United States.
• Vercel — hosting, server logs, anonymous analytics, and routing AI Sensei requests to the AI model.
• Anthropic — Claude generates AI Sensei replies. It receives your messages and the lesson you are on, not your email address or payment details.
• OpenAI — a backup AI model, used for AI Sensei replies only if Claude is unavailable or after a fair-use limit is reached. It receives the same limited information.
• Stripe — subscription payments.
• Resend — sending lesson and account emails.
• Google — only if you choose to sign in with Google.

Cookies

We only use cookies NihonFlow needs to work: your sign-in session, a small flag that sends signed-in learners from nihonflow.com to their dashboard, and your setup choices while you sign up with Google. We use no advertising or tracking cookies.

How long we keep it

We keep your information while your account is open. You can clear an AI Sensei conversation yourself at any time from the chat. If you ask us to delete your account, we delete your account and learning data within 30 days, except records we must keep by law, such as payment records.

Your choices and rights

• Email ahmed@nihonflow.com to access, correct, export, or delete your information.
• Pause lesson emails in Settings or from the link at the bottom of every lesson email.
• Cancel your subscription at any time in Settings.

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. We honour these requests wherever you live.

International transfers

NihonFlow is run from Japan, and our providers store and process data in the United States and other countries. By using NihonFlow, your information is transferred to those countries under each provider’s safeguards.

Children

NihonFlow is not intended for children under 13, and we do not knowingly collect their information. If you believe a child has signed up, email us and we will delete the account.

Security

All traffic uses encrypted connections, and access controls make sure each learner can only reach their own data. No system is perfectly secure, but we work to protect your information and will tell you promptly if a breach affects it.

Changes to this policy

If we change this policy, we will update this page and the date above. For significant changes, we will also email you.

Contact

Questions about privacy: ahmed@nihonflow.com. See also our Terms of Service and About page.