Privacy Policy
Last Updated: 2026-06-15 · Effective: 2026-06-30 · Version: 1.1
Well Rhythm is built on the belief that the most sensitive information you hold deserves a safe place. This policy explains — as plainly as possible — what information we collect, where it is stored, and what we use it for.
1Business Information
The app "Well Rhythm" (the "App") is provided by LO KAHEI (the "Provider"). For enquiries, please contact us from within the app (Settings → Feedback). This Privacy Policy governs the handling of user information in connection with the App and this website.
2Core Principles
Because Well Rhythm handles health-related data, privacy protection and data minimisation are our top priority. We collect and use only the minimum information necessary, based on your consent.
Local-first design. Health records — including symptoms, menstrual cycle, basal temperature, diary, and medication — are encrypted and stored on your device only. They are not sent to or stored on the Provider's servers. The Provider handles only membership information (email address), subscription status, and the encrypted sharing envelope (which we cannot decrypt) when sharing is enabled.
3Information We Collect & How We Use It
The table below describes the information the Provider may collect, its source, storage location, purpose, and retention period. Health data is stored on-device by default; information sent to servers is kept to the minimum required for each feature.
| Category | Source | Storage | Purpose | Retention |
|---|---|---|---|---|
| Health data Cycle, symptoms, basal temp, diary, medication, etc. | User input (optionally imported from the Health app) | On-device only (encrypted) | App features: cycle prediction, correlation analysis, daily message, etc. | Until deleted by user (export & delete available) |
| Email / account information | Provided by user | Provider servers (Japan region) | Registration, login, device migration, support contact | Deleted within 60 days of account deletion (statutory retention may apply) |
| Subscription status | App store integration | App store / Provider servers | Determining paid features, billing management | Per app store terms |
| Sharing envelope Encrypted summary | User's device | Provider servers (relay only, cannot decrypt) | Relaying partner sharing | Retained for a set period (e.g., 30 days) after sharing is disabled, then deleted |
| Approximate location Rounded to ~1 km radius | Device (with permission) | On-device + weather provider Apple Weather (US) | Fetching local barometric pressure & weather | Used in real time; server-side cache for a few minutes only, not permanently stored |
| Access logs Timestamp, IP address, etc. | App usage | Provider servers (linked to email) | Service improvement, security investigation, incident response | 90 days |
| Audit logs Sign-in, sharing activity, etc. | App usage | On-device only (encrypted) | Forensic investigation in case of misuse | 30 days |
Feedback and attached images: Posting from the in-app feedback box (text, and optionally attached images) requires an account (sign-in). Submissions are stored in the Provider's private storage (Japan region) and are moderated (viewed and reviewed) by an administrator to decide whether to publish them. Only submissions the administrator approves are published anonymously on the public board, where images are shown via short-lived signed URLs. If you attach an image, please mask personal information such as names, faces, addresses, or contact details (e.g., black it out) before submitting. The handling of unmasked images containing personal information that are submitted by mistake (rejection of the post, email notification, deletion of the image, and the disclaimer regarding the administrator having viewed it) is governed by the Terms of Service.
4Third-Party Sharing & Processors
Partner sharing: Sharing occurs only when you explicitly enable it. Only a summary and a partner-facing message are shared — not symptom details, diary entries, or specific dates. Shared content is end-to-end encrypted between devices; the Provider relays only the encrypted data and cannot decrypt it. You bear responsibility for how the recipient manages the received information; the Provider is not liable for the recipient's actions except where caused by the Provider's own intentional or grossly negligent conduct.
Processors & partners: The Provider may engage processors for authentication, subscription relay, sharing relay, and weather data retrieval. Appropriate data processing agreements are in place with all processors. Key processors and the information shared are listed below.
| Processor | Information Provided | Purpose & Location |
|---|---|---|
| Apple Inc. (Apple Weather / WeatherKit) | Approximate location only Rounded to ~1 km radius (lat/lon) | Fetching local barometric pressure & weather. Location: US. No health, cycle, or diary data is sent. |
| Amazon Web Services (cloud infrastructure) | Contact info, subscription status, encrypted sharing data, support enquiries | Server operations for auth, subscriptions, and support. Location: Japan region. |
Location data is sent to Apple Weather (US) via the Provider's server solely to fetch weather. Only the approximate location (~1 km radius) is transmitted — no health, cycle, or diary information is included.
5International Transfers
The Provider's backend primarily uses the Japan region and does not store your information on overseas servers. However, approximate location data (~1 km radius) is transmitted to the weather service provider Apple Weather (US) to fetch barometric pressure and weather. Health data itself is never transferred internationally. Where international transfers are required, appropriate safeguards are applied in accordance with applicable law. Only an approximate location rounded to about a 1 km square is transmitted; it is not linked to the email address or user ID held on the Provider's server, to identifying information such as your name, or to any health, cycle, or diary data (it is only relayed to fetch weather and is not permanently stored), and it is not continuously accumulated. Accordingly, the Provider does not treat this coarse location as information that identifies a specific individual (personal information) or as personal-related information, and the recipient, Apple Inc. (US), does not associate this location with you as an individual. The US is not a country designated by Japan's Personal Information Protection Commission as ensuring an equivalent level of protection; however, as noted above, only a non-identifying coarse location is sent, solely to fetch weather. Your use of this feature is treated as your consent to the collection and use of this coarse location.
6Security Measures & Incident Response
The Provider takes reasonable technical and organisational measures to prevent loss, destruction, or unauthorised access to your information.
- On-device encryption of stored data
- Encryption key isolation in the OS secure enclave
- End-to-end encryption for sharing
- Data minimisation and access control
- Consent recording and audit trail management
- Security controls enforced through processor agreements
- Regular vulnerability patching and log auditing
Breach response: In the event of a serious personal data breach, the Provider will promptly notify the relevant authorities and affected users in accordance with applicable law. An incident response procedure is maintained and will be disclosed as necessary.
7Your Rights & Controls
You can export all data (JSON) or permanently delete all data (immediate physical deletion) from Settings → Privacy & Data within the app. Account deletion is also available. You may also request disclosure, correction, suspension of use, or erasure of personal data from the Provider (subject to legal limitations). To submit a request, please contact us from within the app (Settings → Feedback). Consent may be withdrawn at any time; however, withdrawal may affect your ability to use certain features.
8Health Integration (Optional)
HealthKit (iOS) / Health Connect (Android) integration is opt-in (off by default). Only data within the scope you permit is read on-device and is not sent to or stored in the cloud. Integration can be revoked at any time.
- Data we read (only within the scope you permit): menstrual cycle, body weight, height, steps, sleep, resting heart rate, active energy, and symptoms (e.g. cramps, bloating). Used on-device only for cycle prediction and correlation; daily data such as weight through active energy is not stored.
- Write-back (if you turn on two-way sync): period dates you record in the app are saved to your device's Health (HealthKit / Health Connect). They are not sent to the Provider's servers.
- Data read via health integration is not used for advertising or third-party marketing, and is not shared with third parties. The backup feature excludes health-sourced records.
9Tracking & Advertising
We do not engage in tracking for the purpose of identifying or profiling users. If anonymised usage statistics are collected, this will be disclosed in advance and you will have the option to opt out. If advertising is introduced, it will be disclosed in advance, your consent will be obtained, and only the minimum necessary information will be used.
10Age Restrictions
This app is intended for users aged 13 and over. Users under 13 may not use this app. Users aged 13–17 should use the app with parental consent. The app includes an age verification step during onboarding; if the user is under 18, parental consent will be requested.
11Policy Updates
Changes to this policy will be announced via in-app notifications or the app store listing. For significant changes affecting how health data is handled, users will be asked to re-consent and a record of that consent will be retained.
12Contact
For enquiries about this policy, please contact us from within the app (Settings → Feedback) or by email (support@well-rhythm.com). Requests for disclosure, correction, suspension of use, or deletion are accepted at the same contact.
The Japanese text of this policy is the authoritative version; this English translation is provided for convenience only, and the Japanese version shall prevail in the event of any discrepancy.
This policy takes effect on 2026-06-30.