Terms of Service

1. Acceptance of these Terms

These Terms of Service ("Terms") are a binding agreement between you and Kaku ("Kaku", "we", "us", or "our"). They govern your access to and use of:

The Kaku desktop application for macOS and Windows.
The Kaku website and landing page.
The Kaku backend services that the desktop app communicates with.

Together these are the "Service".

By downloading, installing, accessing, or using the Service, you agree to be bound by these Terms and by our Privacy Policy. If you do not agree, do not install or use the Service.

If you are using the Service on behalf of an employer or other organization, you represent that you have authority to bind that organization to these Terms, and "you" in that case means both you personally and that organization.

2. The Kaku Service

Kaku is a desktop assistant for Japanese writing. It runs in the background of supported desktop applications and:

Surfaces inline correction suggestions for sentences you have completed typing, including grammar, particle, vocabulary, and keigo issues.
Provides plain-English explanations for non-trivial corrections.
Offers an on-demand Tone Converter that rewrites selected text into casual, polite, or business-formal Japanese.

The exact features available to you depend on your plan and on the supported applications and operating systems at the time you use the Service. We may add, change, or remove features over time. We will provide reasonable notice for material changes that adversely affect paid features.

3. Eligibility and your account

3.1 Age

You must be at least 13 years old to use the Service. If you are under the age of majority in your jurisdiction, you may use the Service only with the consent of a parent or legal guardian.

3.2 Account creation

You create a Kaku account by signing in with a Google Account. We do not support password-based account creation. Your Kaku account is tied to the Google Account you used to sign in.

3.3 Your responsibility

You are responsible for:

The accuracy of the information associated with your Google Account.
All activity that occurs under your Kaku account.
Keeping your device and Google Account secure.

If you suspect unauthorized access to your account, sign out of all devices from Settings → Account, secure your Google Account, and contact us at kakuprotech@gmail.com.

3.4 One account per person

You may not create more than one Kaku account per person, and you may not share your account credentials.

4. Plans

4.1 Free plan

The Free plan lets you use Kaku up to a daily quota of corrections and tone conversions. The exact quotas are shown in the Kaku desktop app and may change with reasonable notice.

4.2 Pro plan

The Pro plan unlocks unlimited corrections and tone conversions, plus the additional features listed on the Kaku pricing page when you subscribe.

4.3 Plan changes

You may upgrade from Free to Pro, or downgrade from Pro to Free, at any time from Settings → Subscription. Plan changes take effect as described in §5.

5. Billing, renewal, and refunds

5.1 Payment processor

Payments are processed by Stripe, Inc. ("Stripe"). When you provide payment details, you provide them directly to Stripe, and your use of Stripe is governed by Stripe's own terms and privacy policy. Stripe acts as an independent controller of your payment-card data.

Kaku uses Stripe-hosted payment fields, so full payment card numbers and security codes never reach Kaku's servers. Kaku's responsibility for payment-card data is accordingly limited to the applicable PCI-DSS SAQ-A scope; Stripe is responsible for securing the payment-card data it collects and stores.

To the maximum extent permitted by law, Kaku is not liable for any loss, damage, declined or failed transaction, delayed settlement, service interruption, or security incident arising from Stripe's systems, acts, or omissions, including any unavailability of Stripe or any compromise of data held by Stripe. Your sole recourse for such matters is against Stripe under its agreement with you.

5.2 Subscription term

Pro subscriptions renew automatically at the end of each billing period (monthly or annual, depending on the plan you chose) until you cancel. Each renewal is charged to your payment instrument at the price in effect at the start of that renewal period.

By subscribing to Pro, you expressly authorize us, through Stripe, to charge your payment instrument on a recurring basis at the then-current price for each renewal period until you cancel. You acknowledge that your subscription renews automatically. For annual subscriptions, we will send a renewal reminder to your account email between 15 and 45 days before each renewal where required by applicable law. You may cancel at any time from Settings → Subscription, effective at the end of the current billing period.

5.3 Price changes

We may change Pro pricing. If we do, we will notify you at least 30 days before the change applies to your account. If you do not agree to the new price, you may cancel before the change takes effect.

5.4 Cancellation

You can cancel your Pro subscription at any time from Settings → Subscription. Cancellation stops future renewals; it does not refund the current period. After the current period ends your account reverts to the Free plan.

5.5 Refunds and right of withdrawal

Except where required by mandatory law, all payments are non-refundable, and cancellation does not entitle you to a refund of fees already paid for the current billing period. We may, at our sole discretion, grant a pro-rated refund in exceptional circumstances.

If you are a consumer in the European Economic Area or the United Kingdom, you normally have a 14-day right to withdraw from a purchase of digital services. By subscribing and checking the box to begin using Pro immediately, you (a) expressly request that we begin providing the Pro service during the withdrawal period, and (b) acknowledge that you lose your right of withdrawal once the service has been fully performed, and that for partial performance you may owe an amount proportionate to the service already provided. Where this waiver is not validly obtained, your statutory withdrawal right is unaffected.

5.6 Taxes

Prices shown are exclusive of any taxes, levies, or duties imposed by your jurisdiction unless explicitly stated. You are responsible for any such taxes.

5.7 Disputed charges and chargebacks

If you believe a charge is incorrect, contact us at kakuprotech@gmail.com before initiating a chargeback or payment dispute, and we will work in good faith to resolve it. Initiating a chargeback or payment dispute for a charge that was properly authorized and rendered (a) is a breach of these Terms, and (b) entitles us to immediately suspend or terminate your account and Pro access.

You agree to reimburse us for any chargeback, dispute, or reversal fees we incur in connection with a dispute later found to be invalid, together with the disputed amount. We may set off such amounts against any refund or credit otherwise owed to you. Nothing in this section limits your statutory rights or your right to dispute a charge that was genuinely unauthorized or erroneous.

5.8 Failed or declined payments

If a renewal payment fails, we (through Stripe) may retry the charge over a grace period of up to 14 days. If payment is not successfully collected within that period, your account will revert to the Free plan and Pro features will be disabled until a valid payment is made. We are not responsible for any loss of access resulting from a payment instrument that is expired, declined, or has insufficient funds. Keeping a valid payment method on file is your responsibility.

6. License to use Kaku

Subject to your compliance with these Terms, Kaku grants you a personal, non-exclusive, non-transferable, non-sublicensable, revocable license to install and use the Kaku desktop application on devices you own or control, for your own personal or internal business use.

We retain all right, title, and interest in and to the Service, including all software, trademarks, logos, content we publish, and underlying intellectual property. Nothing in these Terms transfers ownership of any Kaku intellectual property to you.

7. Your content

7.1 What we mean by "your content"

"Your content" is any text you submit to the Service for processing, including text you select for tone conversion and any text accompanying a feedback rating you choose to submit. "Your content" does not include text the on-device correction engine processes locally — that text never reaches our servers.

7.2 Ownership

You retain ownership of your content. These Terms do not transfer any ownership rights in your content to us.

7.3 License you grant us

You grant Kaku a worldwide, royalty-free, non-exclusive license to:

Transmit, process, and display your content as needed to provide the Service to you (for example, sending a selected passage to our large language model provider and returning the rewritten result to you).
Where you explicitly submit a thumbs-up or thumbs-down feedback rating, store the submitted source and converted text for the purpose of improving the quality of our correction and tone-conversion models, under the conditions described in the Privacy Policy.

This license ends when we delete the relevant content under the retention rules in the Privacy Policy, or when you delete your account, whichever comes first.

7.4 Your representations

You represent and warrant that you have the right to submit any content you send to the Service, and that your content does not infringe anyone else's rights or violate any law.

8. Acceptable use

You agree not to:

Use the Service for any unlawful purpose, or to generate or distribute unlawful content.
Submit content that infringes the intellectual property rights, privacy rights, or other rights of any third party.
Probe, scan, reverse-engineer, decompile, disassemble, or attempt to extract source code from the Service, except to the extent applicable law expressly permits this despite a contractual prohibition.
Use the Service to build a competing product or train a competing AI model.
Send automated requests at a rate or volume that interferes with normal operation, or that exceeds your plan's quotas.
Attempt to circumvent rate limits, plan enforcement, authentication, or any other security or access controls.
Resell, rent, lease, or otherwise commercially exploit the Service except as expressly permitted.
Use the Service to send spam, harassing content, or content that violates applicable export control laws.
Impersonate another person or misrepresent your identity in connection with the Service.

We may suspend or terminate accounts that violate this section under §11.

9. AI suggestions and accuracy disclaimer

Kaku surfaces suggestions produced by rule-based logic and by large language models. These suggestions are not guaranteed to be accurate, appropriate for your context, or free of error.

A correction Kaku surfaces may itself be incorrect, or may be technically valid but unsuitable for the relationship, register, or industry conventions you are writing within.
A tone-converted result may misinterpret the source passage or produce phrasing that is grammatical but awkward.
You remain responsible for reviewing every suggestion before applying it, and for the final content you choose to send.

Kaku is a writing assistant. It does not replace human judgment, professional translation, or legal, medical, financial, or other expert advice.

10. Third-party services

The Service relies on the following third-party services:

Google for OAuth sign-in.
Stripe for payment processing.
Our large language model provider for cloud tone-conversion inference.
A third-party cloud hosting provider for hosting our backend.

Your use of those services through Kaku is also subject to their respective terms and privacy policies. We are not responsible for the practices of those third parties beyond our contractual relationship with them.

11. Suspension and termination

11.1 By you

You may stop using the Service at any time. You may delete your account from Settings → Account → Delete account. Deletion takes effect as described in the Privacy Policy §7.

11.2 By us

We may suspend or terminate your account, with or without notice, if:

We reasonably believe you have violated these Terms.
Your account or device is compromised in a way that risks other users or the Service.
We are required to do so by law or by valid legal process.
We discontinue the Service or a material portion of it (in which case we will give reasonable advance notice and refund any unused prepaid Pro fees on a pro-rata basis).

11.3 Effect of termination

When your account is terminated, your right to use the Service ends. Sections that by their nature should survive termination — including §5.7 (chargeback and reimbursement obligations), §6 (license, residual ownership), §7.3 (license to feedback content already stored), §9 (disclaimer), §12 (disclaimers), §13 (limitation of liability), §14 (indemnification), and §15 (governing law) — survive.

12. Disclaimers of warranty

To the maximum extent permitted by applicable law:

The Service is provided "as is" and "as available", without warranty of any kind, whether express, implied, or statutory, including any implied warranties of merchantability, fitness for a particular purpose, title, non-infringement, or accuracy.

We do not warrant that:

The Service will be uninterrupted, secure, or error-free.
Corrections or tone-converted output will be accurate, complete, or appropriate for your use.
Defects in the Service will be corrected within any particular timeframe.

Some jurisdictions do not allow exclusion of implied warranties; in those jurisdictions the above exclusions apply only to the extent permitted by local law.

13. Limitation of liability

To the maximum extent permitted by applicable law:

In no event will Kaku, its affiliates, officers, employees, agents, or service providers be liable to you for any indirect, incidental, special, consequential, exemplary, or punitive damages, or for any loss of profits, revenue, data, or business opportunity, arising out of or relating to your use of, or inability to use, the Service, even if advised of the possibility of such damages.
The total aggregate liability of Kaku for all claims arising out of or relating to these Terms or the Service will not exceed the greater of (a) the amount you paid to Kaku for the Service in the twelve months immediately preceding the event giving rise to the claim, or (b) ¥10,000.

These limits apply to all theories of liability — contract, tort (including negligence), strict liability, or otherwise. They do not apply to liability that cannot be limited under applicable law (for example, liability for gross negligence, willful misconduct, or death or personal injury caused by negligence, in jurisdictions where those limits are prohibited).

14. Indemnification

You agree to indemnify, defend, and hold harmless Kaku and its affiliates, officers, employees, agents, and service providers from and against any claim, demand, loss, liability, damage, or expense (including reasonable legal fees) arising out of or relating to:

Your breach of these Terms.
Your content or your use of the Service.
Your violation of any applicable law or third-party right.

We will promptly notify you of any such claim and reasonably cooperate with your defense, and you may not settle any such claim in a way that imposes liability on us without our prior written consent. We may, at our option and expense, assume the exclusive defense and control of any matter otherwise subject to indemnification by you, in which case you agree to cooperate with our defense of that claim.

15. Governing law and disputes

These Terms, and any dispute arising out of or relating to these Terms or the Service, are governed by the laws of Japan, without regard to its conflict-of-laws principles.

You and Kaku agree that any dispute will be resolved exclusively in the courts of Tokyo, Japan (the Tokyo District Court as the court of first instance), and you and we each consent to the personal jurisdiction of those courts.

Nothing in this section prevents either party from seeking injunctive or other equitable relief in any court of competent jurisdiction to protect its intellectual property rights or confidential information.

If you are a consumer resident in a jurisdiction that grants mandatory consumer-protection rights, this section does not deprive you of any protection granted to you by mandatory provisions of the law of the country in which you reside.

16. Changes to these Terms

We may update these Terms from time to time. If we make a material change, we will:

Post the revised Terms on this page and note the date of the latest revision.
Notify signed-in users by email or in-app message at least 30 days before the change takes effect.

Continued use of the Service after the change becomes effective constitutes acceptance of the updated Terms. If you do not agree, your remedy is to stop using the Service and cancel your account before the change takes effect.

17. Miscellaneous

Entire agreement. These Terms, together with the Privacy Policy, are the entire agreement between you and Kaku regarding the Service, and they supersede any prior agreements.
No waiver. Our failure to enforce any provision is not a waiver of our right to enforce it later.
Severability. If any provision is held unenforceable, the rest of these Terms remain in force, and the unenforceable provision is to be modified to the minimum extent needed to make it enforceable while preserving its intent.
Assignment. You may not assign these Terms or any rights under them without our prior written consent. We may assign these Terms in connection with a merger, acquisition, sale of assets, or by operation of law.
No agency. Nothing in these Terms creates a partnership, joint venture, employment, or agency relationship between you and us.
Notices. Notices to you may be sent to the email address on your account or shown in-app. Notices to us must be sent to kakuprotech@gmail.com.
Force majeure. Neither party is liable for delay or failure caused by events beyond its reasonable control.
Language. These Terms are written in English. Where a translation is provided, the English version controls in case of conflict, except where applicable consumer-protection law requires otherwise.

18. Contact

For questions about these Terms:

Kaku Email: kakuprotech@gmail.com

For privacy questions, see the Privacy Policy.