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Hitaru

Terms of Service (Draft)

Last updated: 2026-08-10

These Terms of Service ("Terms") govern your use of Hitaru (the "Service"), which is operated by an individual sole proprietor based in Japan (the "Operator"). By using the Service, you agree to these Terms.

  1. By creating an account or using the Service, you are deemed to have agreed to these Terms.
  2. If you do not agree to these Terms, you may not use the Service.
  3. Minors may use the Service only with the consent of a parent or legal guardian. Users under 13 may not use the Service without a parent or legal guardian's consent.
  1. Hitaru is a language-learning aid that lets you save English expressions with one tap while watching English-language Netflix content (primarily titles with English audio, English subtitles, and Japanese subtitles) and review them later using spaced repetition (SRS).
  2. The Service consists of (a) a Chrome extension that runs while you watch Netflix, (b) a mobile app (iOS / Android) for spaced-repetition review, and (c) a temporary relay server used to transfer cards between the extension and the app.
  3. The "commentary" the Service provides consists of dictionary-style definitions, grammar notes, and nuance explanations — it is not a full translation of the subtitle dialogue. See Section 7 (Handling of Subtitles, Translation, Images, and Audio) for details.
  4. The features of the Service may change, be added, or be removed without prior notice due to technical reasons, changes on Netflix's side, or legal requirements.
  1. Use of the Service requires that you hold your own valid Netflix subscription.
  2. The Service is an independent third-party service and is not an official partner, agent, or affiliate of Netflix, Inc. "Netflix" and related trademarks belong to their respective owners.
  3. The Service is an assistive tool that displays a learning overlay on top of the Netflix playback screen; it does not modify the Netflix service itself. It does not perform automated access or scraping (such as automated login or automated continuous playback) of the kind prohibited by Netflix's Terms of Use.
  4. Changes on Netflix's side — to its technical specifications, content lineup, or terms of use — may render part or all of the Service unavailable without notice. The Operator's liability for resulting damages is limited as set out in Section 11 (Limitation of Liability).
  1. Using the Service requires registering an account. Accounts can be created with an email address or via Google OAuth through Supabase Auth (additional OAuth providers are planned).
  2. You must keep your registration information accurate and are responsible for safeguarding your password and other credentials. If you discover unauthorized use of your account, contact us immediately using the contact details in Section 16.
  3. Cards are transferred between the desktop extension and the mobile app through an end-to-end encrypted (E2EE) temporary relay, with the encryption key exchange performed via your authenticated login (no manual QR-code pairing step). Relay data is held only for a short period and is automatically deleted after that; once deleted, it can no longer be decrypted.
  4. Creating multiple accounts to circumvent free-tier limits or anti-abuse measures is prohibited (see Section 6).
  1. The Service offers a Free plan and a Pro plan; see https://hitaru.dev/pricing for current pricing. The Free plan lets you use, at no charge with ads, the subtitle-and-commentary overlay (including the Chrome extension's one-tap save and sending cards to your phone) and automatic review reminders; the Pro plan is a paid plan that adds ASR-generated subtitles, unlimited episodes and card creation, and an ad-free experience.
  2. Pro plan pricing operates within the range of $8–$12/month (reference: approx. ¥1,200–¥1,500) and $79–$99/year (reference: approx. ¥9,800–¥12,800). The actual price shown at signup on the Web LP may include a limited first-year promotional annual price (reference: ¥9,800); this promotional price applies only to the first year and may be revised to the standard range in subsequent years.
  3. Payments are processed through our payment processor, Stripe. We do not store your credit card number or other payment credentials ourselves. During the initial launch phase, Pro plan purchases are handled exclusively through the Web LP; the mobile app does not offer in-app purchases.
  4. Subscriptions renew automatically. You may cancel at any time before the next renewal date, after which billing stops from the following renewal date onward. Except where a refund is legally required, amounts already paid are non-refundable (including on a pro-rated basis). If a technical malfunction prevented you from using the Service within 7 days of your first use, please contact support; refund requests made under Japan's Act on Specified Commercial Transactions will be handled within the scope required by law.
  5. Prices may be revised due to currency fluctuations or other business circumstances. Price increases for existing subscribers generally take effect from their next renewal and will be announced in advance.
  1. Reverse-engineering or decompiling the Service, or unauthorized automation, scraping, or misuse of its APIs
  2. Reselling, redistributing, or publicly sharing commentary, cards, or other content obtained through the Service (including via shared Anki decks or similar)
  3. Creating accounts that impersonate others, or abusing the free tier through fraudulently obtained multiple accounts
  4. Unauthorized access, probing or attacking vulnerabilities, circumventing rate limits, or otherwise interfering with the operation of the Service
  5. Using the Service to generate or distribute copyright-infringing content, or any other conduct that violates applicable law
  6. If a violation is confirmed, the Operator may restrict features, suspend, or terminate the account, with or without prior notice (see Section 12).
  1. The Service reads and displays Netflix's subtitle text (both English and Japanese) locally in your browser only; it does not transmit or store the subtitle text on our servers.
  2. The "commentary" the Service generates consists of our own explanations of word/phrase meaning, grammar, nuance, and cultural context; it does not create, store, or provide a full translation of the dialogue. Any quotation of original dialogue within commentary is limited to what satisfies the quotation requirements of Article 32 of Japan's Copyright Act (necessity of purpose, clear separation from original commentary, commentary as the primary content, attribution of source, and no alteration).
  3. As a narrow exception, for titles that lack an official Japanese subtitle track, or where a mislabeled or mixed-language subtitle track is detected, the Service may temporarily cache machine-translated text. This cache is keyed only by a one-way hash of the source line, is never linked to your account, and is automatically deleted after at most 30 or 90 days depending on the case.
  4. Screenshots and similar images you capture pass through our servers only temporarily, for at most 5 minutes, while end-to-end encrypted (E2EE), and are deleted immediately once transfer to the mobile app completes. The Operator cannot decrypt or view the content of this encrypted data. When you tap the star (save) button to create a card, the Service also captures a short audio clip corresponding to the sentence you save. This audio clip is likewise end-to-end encrypted and passes through our servers only temporarily before being automatically deleted after a short period; the Operator cannot decrypt or view its content.
  1. Copyright in the commentary and other content generated by the Service belongs to the Operator. You may use this content for your own personal learning purposes, but may not redistribute, share, or commercially exploit it.
  2. Copyright in Netflix's content (video, audio, subtitles, etc.) belongs to Netflix and its respective rights holders. The Service uses excerpts of this material only within the limited scope permitted by quotation and similar provisions of copyright law.
  3. You retain rights in the data you create or submit through the Service (study cards, settings, etc.). The Operator uses this data only to the extent necessary to provide the Service.
  4. Rights in the Service's trademarks, logos, and design belong to the Operator or the applicable rights holder.
  1. The Service relies on third-party services including Stripe (payment processing), Supabase (authentication and database), Cloudflare (content delivery and API infrastructure), Upstash (rate limiting), PostHog (behavioral analytics), Sentry (error monitoring), Resend (email delivery), a third-party push notification service (mobile app notifications), and the OpenAI, Anthropic, and Google LLM APIs (commentary generation).
  2. These third-party services are governed by their own terms of use and privacy policies. The Operator has reviewed its arrangements with each provider as appropriate.
  3. Outages, specification changes, or discontinuation of a third-party service may render part of the Service unavailable.
  1. The Service is provided "as is" without any warranty of fitness for a particular purpose, completeness, or continuity.
  2. Learning outcomes (including improvements to test scores such as TOEIC) vary by individual and are not guaranteed.
  3. The Operator is not responsible for the Service becoming unavailable due to changes in Netflix's specifications, content, or availability.
  4. The Operator is not responsible for interruptions or suspensions of the Service caused by events reasonably beyond the Operator's control, such as natural disasters, communication failures, or third-party service outages.
  1. Except where caused by the Operator's willful misconduct or gross negligence, the Operator's liability for damages arising from your use of, or inability to use, the Service is limited to direct, ordinary damages actually incurred, and is capped at the total amount you paid for the Service in the preceding 12 months.
  2. To the extent permitted by law, the Operator is not liable for lost profits, indirect damages, special damages, loss of data, or other consequential damages.
  3. This Section does not apply to the extent it would be void under Japan's Consumer Contract Act or other mandatory law. The Operator will not invoke the limitations in this Section for damages caused by its own willful misconduct or gross negligence.
  1. You may request to cancel the Service or delete your account at any time. See Section 8 of the Privacy Policy for details of the process.
  2. If you violate these Terms (in particular Section 6, Prohibited Conduct), the Operator may restrict features on, suspend, or terminate your account, with or without prior notice.
  3. Accounts found to have repeatedly infringed copyright will be suspended in accordance with our Repeat Infringer Policy (/legal/repeat-infringer), which is incorporated into this Section by reference.
  4. How your data is handled after account suspension or termination (retention period and deletion schedule) is governed by Section 8 of the Privacy Policy.
  1. Rights holders who identify content that infringes copyright or other rights may contact us via our takedown request form (/legal/takedown) or at copyright@hitaru.dev.
  2. We aim to send an automated acknowledgment within 1 hour of receipt, complete initial review within 24 hours, and reach a removal decision within 72 hours.
  3. Hitaru does not currently maintain a registered DMCA Designated Agent with the US Copyright Office. Takedown requests are handled primarily under Japan's Act on the Limitation of Liability for Damages of Specified Telecommunications Service Providers ("Information Distribution Platform Act") and EU DSA Art. 16 procedures. We do not currently claim the DMCA §512 safe harbor.
  4. See our Repeat Infringer Policy (/legal/repeat-infringer) for how accounts with confirmed repeat infringement are handled.
  1. These Terms are governed by the laws of Japan.
  2. Any dispute between you and the Operator arising in connection with the Service is subject to the exclusive jurisdiction of the Tokyo District Court as the court of first instance.
  3. Even if the Operator incorporates a legal entity in the future, the governing law and jurisdiction for existing usage agreements will remain as set out in this Section unless changed through notice to users and an amendment of these Terms.
  1. The Operator may revise these Terms from time to time. For material changes, we will provide at least 30 days' advance notice before the changes take effect, by updating this page and notifying you at your registered email address.
  2. If you do not agree to the revised Terms, you may stop using the Service and cancel your account. If you continue using the Service after a material change takes effect, you are deemed to have agreed to the revised Terms.
  3. Where a change differs materially from the prior Terms, you may be asked to re-affirm your consent within the Service.
  1. If any provision of these Terms is held invalid under applicable law, the remaining provisions will continue in full force and effect.
  2. Questions about these Terms can be sent to support@hitaru.dev.
  3. The Japanese version of these Terms is the controlling version. The English version is provided for your convenience; in case of conflict, the Japanese version prevails.