Privacy Policy

1. Introduction

Kusari ("we", "us", "our") is an English learning application operated by Ryuta Abe (sole developer). This Privacy Policy explains what information we collect when you use the Kusari iOS / Android application or our website, why we collect it, and how it is handled.

By creating an account or using Kusari, you agree to this policy.

2. Information we collect

2.1 Account information

• Email address (for sign-in, password recovery, transactional notifications)
• Encrypted password (stored by our authentication provider, never visible to us)

2.2 Learning activity data

• Daily completion records (which of the three steps you finished, timestamps, timezone)
• Streak counts and rolling 30-day cycle data
• Practice problem prompts, your written answers, and AI-generated correctness judgments
• Spaced-repetition (SRS) card history and review quality
• AI conversation transcripts (text only — see 2.3 for audio handling)

2.3 Voice / microphone audio

When you use Step 1 (AI Conversation), Kusari records short audio clips (typically 5–30 seconds) from your device microphone. These recordings are sent to our backend and forwarded to OpenAI's transcription service to convert speech to text. After transcription, audio is discarded. We do not retain raw audio files.

2.4 Subscription and purchase information

• Purchase status, subscription tier, renewal dates, and entitlement state (provided by Apple App Store / Google Play and our subscription provider RevenueCat)
• We do not receive or store credit card numbers, bank details, or other payment instruments

2.5 Diagnostic data

Crash logs and basic application diagnostics may be collected by Apple App Store Connect / Google Play Console for product reliability. This data is anonymized.

3. How we use information

• To provide the core service (track progress, generate practice problems, evaluate answers, manage SRS cards)
• To compute your discount tier for the next billing cycle
• To process and renew your subscription
• To respond to support inquiries
• To improve service reliability via diagnostic logs

4. Third parties (sub-processors)

We share the minimum necessary data with:

• Supabase (authentication and database hosting) — stores your email, encrypted password, and learning activity data.
• OpenAI (AI processing) — receives short conversation audio for transcription, and conversation / practice text for generation and grading. OpenAI does not retain API request data for training (per OpenAI API policy).
• Cloudflare (backend hosting) — proxies API requests; logs request metadata such as IP and user agent for security.
• RevenueCat (subscription management) — receives anonymized subscription state for entitlement checks.
• Apple App Store / Google Play — handles all payment processing.

We do not sell your personal data.

5. Data retention

• Account and learning data: kept until you delete your account.
• Audio recordings: not retained after transcription.
• Subscription records: retained for legal and tax requirements after subscription ends.

6. Your rights

You may at any time:

• Request a copy of the personal data we hold about you
• Request correction of inaccurate data
• Request deletion of your account and associated data
• Withdraw consent (which terminates the service)

To exercise these rights, contact us at the address below. Account deletion will remove email, learning history, and SRS data within 30 days.

7. Children

Kusari is not directed to children under 13. We do not knowingly collect personal information from children under 13.

8. Security

We use HTTPS for all API traffic, encrypted password storage, and access controls. No internet service is 100% secure; we make no absolute guarantee but take reasonable measures.

9. International users

Kusari is operated from Australia. By using the service from outside Australia, you consent to your data being transferred to Australia and to the third-party processors listed in section 4 (which may operate in the United States or other regions).

10. Changes to this policy

We may update this policy. Material changes will be communicated via email or in-app notice. Continued use after the effective date constitutes acceptance.

11. Contact