Terms of Service

1. Agreement to these terms

Koboshi (“Koboshi”, “we”, “us”) is a vocabulary-learning service operated by an individual operator based in Japan. By creating an account or using the service in any way, you agree to these Terms of Service and to our Privacy Policy. If you do not agree, please do not use Koboshi.

The operator's name and address are provided without delay upon request to support@koboshi.app. They are not printed here because Koboshi is run by one person and those are personal details; ask and you get them in writing, promptly. You never have to agree to terms without being able to find out exactly who you are agreeing with.

2. What Koboshi is, and what it is not

Koboshi helps you look up, save, and review vocabulary across several languages. It uses spaced repetition to decide when to show you a word again, and it uses an AI language model to generate meanings, examples, and related material.

It is a study aid. It is not a teacher, not a certified translator, and not a substitute for a dictionary you can cite. Do not rely on it for anything that matters legally, medically, commercially, or academically without checking the answer somewhere authoritative.

4. Who can use Koboshi

You must be at least 13 years old to use Koboshi, anywhere in the world. Koboshi is a general-audience study tool and is not directed at children.

When you set up your account we ask for the month and the year you were born, and an answer under 13 cannot finish setting up. We store only that month and year, never a full date of birth. If we learn that an account belongs to someone under 13, we will delete that account and its learning data. If you are a parent or guardian and believe your child holds an account, email us at support@koboshi.app and we will remove it.

5. Your account

You sign in with Google or with an email link. One account per person. You are responsible for keeping access to your sign-in method secure and for what happens under your account. Tell us promptly at support@koboshi.app if you believe someone else has got into it.

6. Free during beta, and the free-plan promise

Koboshi is free while it is in beta. There is no card, no trial timer, and no charge.

Our promise for later: there will always be a free plan, and we will never start charging you without asking first. Concretely, that means two commitments we hold ourselves to:

• Your account is never flipped from free to paid. If paid plans arrive, an existing free account stays free unless you actively choose to upgrade. Silence is never consent, and a notice email is never an upgrade.
• A genuinely usable free plan keeps existing. Saving words, reviewing them with spaced repetition, and quizzing yourself stay available on the free plan. A paid plan, if it comes, adds things on top; it does not take the core away.

This promise is deliberately excluded from our right to change these terms in section 16. We cannot edit our way out of it.

Fair-use limits do apply while we are free: there are daily caps on AI lookups and on screenshot extraction, because each one costs us real money. We may adjust those caps, and we will not make them so tight that normal personal study stops working.

7. Acceptable use

You agree not to:

• use Koboshi for anything unlawful, or in breach of these terms;
• bulk-query, scrape, mirror, or otherwise try to reconstruct our dictionary data, whether by hand, by script, or by any automated means;
• work around a rate limit, a usage cap, or an account limit, including by creating extra accounts to get more free lookups;
• probe, scan, or try to reach accounts, systems, or data that are not yours, or interfere with the service or with anyone else's use of it;
• rely on Koboshi's output for professional translation, certification, examinations, or any other high-stakes purpose;
• use the AI features to generate material that our AI provider's usage policy forbids, including content that sexualises minors, incites violence or terrorism, harasses or threatens people, promotes self-harm, produces malware or weapons instructions, generates fraud or disinformation, or impersonates a real person;
• upload malware, or content that is illegal, infringing, or abusive;
• abuse the flag free-text box, for example to send abuse or to post other people's information;
• reverse-engineer, resell, or commercially exploit the service without our written permission.

We may apply usage limits, throttle requests, or suspend an account we reasonably believe is doing any of the above or putting the service at risk.

8. Your content, and what we may do with it

The words you save, your notes, and your study history are yours. You keep every right you have in them. You give us a narrow licence to host, store, copy, and process that content for one purpose only: running the service for you, for example scheduling your reviews, generating a lookup, and showing you your own library and statistics. Nothing broader.

Separately and specifically: when you flag a problem, or confirm that two words mean the same thing across languages, you allow us to use that report or confirmation to improve our shared dictionary and our cross-language links, in a form that is not linked to you and cannot be traced back to you. That is the one place your activity feeds something other users see, and it is limited to dictionary content.

We do not sell your personal content, and we do not put your private writing into any commercial or research dataset. See the Privacy Policy for the full picture.

9. What you send us: flags and screenshots

When you flag a card, we receive the category, whatever you typed, a snapshot of what was on your screen at that moment, and for some categories a small image of the flagged card. When you use "add words from a screenshot", you send us an image that we pass straight to our AI provider and never store.

By sending either, you confirm that:

• you have the right to send it;
• it does not contain other people's personal information;
• it does not contain identity documents, medical records, or financial records;
• it does not contain copyrighted material you have no right to upload.

Please crop before you upload. Flag screenshots are deleted automatically after 14 days; the exact handling of both kinds of image is set out in the Privacy Policy.

10. Our intellectual property

The Koboshi name, the Koboshin mascot, the logo, the design, the software, and the underlying spaced-repetition and concept-linking systems belong to us or our licensors. These terms give you no right to use our branding or to copy the service beyond what is expressly allowed here.

11. Third-party services

Koboshi runs on services we do not own: hosting, database and authentication, an AI language model, and text-to-speech. They are named, with their roles and countries, in the Privacy Policy. Your use of Koboshi can be affected by their terms and their outages, and we are not responsible for their acts or omissions.

12. Availability, and changes to the service

We work to keep Koboshi up, but it is provided on an “as available” basis, and during beta especially it may break, change, or go down for maintenance. We may add, change, or remove features. If we ever shut the service down or remove something you depend on, we will give you reasonable notice and a way to get your data out first.

13. Disclaimers, and what we do promise

To the fullest extent the law allows, Koboshi is provided “as is” and “as available”, without warranties of any kind, express or implied, including implied warranties of merchantability, fitness for a particular purpose, accuracy, and non-infringement. We do not warrant that the service will be uninterrupted, error-free, or secure, or that any generated content is accurate or complete.

What we do promise is to act with reasonable care. Nothing in this section, or anywhere else in these terms, excludes or limits liability that cannot lawfully be excluded, and nothing here removes any right the consumer law of your own country gives you.

On data loss specifically, we would rather be blunt than reassuring: your data sits in our database provider's backups, but backups are for disaster recovery and we do not offer per-user restore. The practical remedy for losing your work is to export your data, not to claim compensation for it. Ask us for an export any time.

14. Limitation of liability

To the fullest extent the law allows, we are not liable for indirect, incidental, special, consequential, or punitive damages, or for loss of profit, goodwill, or business opportunity, arising from your use of, or inability to use, the service.

Where we are liable, our total liability to you for all claims taken together is limited to the greater of: (a) what you have paid us in the 12 months before the claim arose, or (b) JPY 10,000.

These limits do not apply to liability caused by our intentional acts or our gross negligence, to death or personal injury caused by our negligence, to fraud or fraudulent misrepresentation, or to anything else that cannot lawfully be limited. If you are a consumer, this section is read subject to the mandatory consumer-protection law of your own country, and any part of it that conflicts with that law does not apply to you.

15. Indemnification

If a third party brings a claim against us because you broke these terms, misused the service, infringed someone's rights, or uploaded something you had no right to upload, you agree to cover the reasonable costs and damages we incur as a result, provided we tell you about the claim promptly and let you take part in defending it. This does not apply to anything caused by our own act or omission, and if you are a consumer it applies only to the extent your local law allows.

16. Changes to these terms

We may change these terms when there is a real reason to: a change in the service, a change in the law, a new feature, a new provider, or a security need. For a material change we will update the effective date at the top and tell you in the app or by email before it takes effect, and you are free to stop using Koboshi and export your data instead of accepting it. Every version of this page is kept in our public source history.

The free-plan promise in section 6 is carved out of this section entirely. We cannot change these terms in a way that takes it away.

17. Ending your account

You can stop using Koboshi at any time and ask us to delete your account and its data; email support@koboshi.app and we will do it, along with everything described in the Privacy Policy.

We may suspend or end your access if you break these terms, if you put the service or other users at risk, or if we are legally required to. Except where telling you would itself be unlawful or unsafe, we will say why and give you an email route to challenge it: reply to us and a person will actually look at it. We will also delete an account we learn belongs to someone under 13, as set out in section 4.

Sections that should outlive the account do so: intellectual property, the disclaimers, the limitation of liability, indemnification, and governing law.

18. If we ever transfer the business

Koboshi is currently run by an individual. The operation, including these terms, the service, and the user accounts, may be transferred to a company controlled by the same operator, or to a successor in a merger or sale. We are telling you now so it is never a surprise. If that happens, the same purposes and the same promises in these terms and in the Privacy Policy continue to apply, we will notify you, and you will have the chance to export your data or delete your account first.

19. Governing law and disputes

Talk to us first. If something goes wrong, email support@koboshi.app and we will try to resolve it informally within 30 days. Most things end there.

These terms are governed by the law of Japan, and we agree that the Tokyo District Court is the first agreed forum for any dispute. If you are a consumer, this does not take away your rights: you keep the mandatory protections of the law where you live, and you keep the right to bring a claim in your local courts where that law gives it to you.

There is no arbitration clause here and no class-action waiver. We are not asking you to give up the right to go to court.

• European Economic Area and the United Kingdom. You keep the mandatory consumer protections of the law where you live, and the right to bring a claim in your local courts where that law gives it to you.
• Japan. These terms are governed by the law of Japan, and the Tokyo District Court is the first agreed forum for any dispute.
• United States, including California. There is no arbitration clause here and no class-action waiver. We are not asking you to give up the right to go to court.
• Everywhere else. Wherever you live, section 14 is read subject to the mandatory consumer-protection law of your own country, and any part of it that conflicts with that law does not apply to you.

20. Odds and ends

These terms, together with the Privacy Policy, are the whole agreement between us about Koboshi. If a court finds one part unenforceable, the rest stays in force. Our not enforcing something once does not mean we have given it up. You may not transfer your account or these terms to anyone else; we may transfer them only as described in section 18.

21. Contact

Questions about these terms, a request for the operator's name and address, or anything else: support@koboshi.app. A person reads it.