The short version, in plain English.
Last updated · October 14, 2026
What yen-yen is
yen-yen is a budgeting tool made by kensaurus LLC. It is not a bank, not a financial advisor, and not a tax-filing service. It does not move money. The numbers it shows you are based on what you (or your household) enter — we don't connect to your bank.
Your account
You sign in with one account that works in all our apps. "Our apps" means the apps made by kensaurus LLC, listed at kensaur.us. You must be 16 or older to use yen-yen. If you are under 18, get a parent's or guardian's OK before you buy a paid plan. Keep your sign-in safe. Tell us at once if you think someone else is using it.
Your data
You own your data. You can export, edit, or delete it anytime. We don't sell it, use it for ads, or use it to train AI models. We share it only with the service providers listed in the Privacy policy — for hosting, sync, payments, notifications, error reports and AI features — so they can run yen-yen for us. The Privacy policy says what each one may do with it.
Your household
Anyone you invite to a household can see and change its ledger. Invite only people you trust, and be kind to whoever else is in your household.
Accuracy
You're responsible for the accuracy of what you enter. If you transcribe a number wrong, the ledger will be wrong. The AI features try to be careful, but their results can be wrong, so check them — we never auto-write to your ledger without your tap. Nothing in yen-yen is financial, tax or legal advice.
Other companies' names and logos
yen-yen shows the names and logos of card networks, banks and payment services, such as Visa, Mastercard, JCB, American Express, PayPal and Apple Pay, in their brand colours, to help you tell your accounts apart. These names, colours and logos are trademarks of their owners. We show them in the app only to identify your accounts. None of these companies is affiliated with yen-yen, and none sponsors or endorses it. If you own one of these marks and want us to remove it or change how we show it, email kensaurus@gmail.com. We will remove or change it promptly.
Plans and payments
yen-yen has a free plan. Paid plans are sold through Apple, Google or Stripe. A subscription renews until you cancel it with the store you paid, and you can cancel anytime: you keep the plan until the end of the period you paid for and are not charged again. Paid plans are a digital service, so a period you already paid for is not refunded, except where the law requires it. For Apple and Google purchases, refunds are handled by that store under its own rules. Deleting your account cancels a Stripe subscription for a household you own, but not an Apple or Google one, or a Stripe one you pay for someone else's household.
Service changes
We can suspend abusive or fraudulent accounts (rare, but it happens) and we can discontinue the service with reasonable notice (we don't plan to).
Law and disputes
Japanese law governs these terms. If there is a dispute, the Tokyo District Court hears it first. If you use yen-yen as a consumer, this doesn't take away the protection the law of the country where you live gives you, or your right to bring a claim in a court there or in any other court the law lets you use. Before going to court, please email us — most problems are easier to fix that way.
Who runs yen-yen
kensaurus LLC (ｋｅｎｓａｕｒｕｓ合同会社), Shibuya Dogenzaka Tokyu Bldg. 2F-C, 1-10-8 Dogenzaka, Shibuya-ku, Tokyo 150-0043, Japan. Representative: Kenji Sakuramoto (櫻元 賢次). Legal notice under the Act on Specified Commercial Transactions (特定商取引法に基づく表記): kensaur.us/yen-yen/legal/sctl
Changes to these terms
When we change these terms, we update the date at the top. If a change is significant, we tell you in the app before it takes effect. These terms are written in English. If a translation differs, the English text applies.
The plain-English summary above is what we actually mean. If you need the long-form legal language for your records — for an employer's expense-policy review, for example — email kensaurus@gmail.com and we'll send the same document, formatted with section headers, the same week.