Accused of Trademark Infringement in Japan? How to Respond to a Warning Letter or an Amazon/Rakuten Complaint

"We received a warning letter from a Japanese company saying our brand infringes their trademark." "Our Amazon Japan listing was taken down after an IP complaint." "Do we have to stop selling right away?"

Overseas sellers entering the Japanese market face these situations more and more often. In this article, Japanese Patent Attorney Toru Kano of BrandAgent explains what to do when you are told you infringe a Japanese trademark — what to check first, when it is not infringement, and the options you actually have.

*This article is general information, not legal advice on a specific case (last updated: October 2026).

What you will learn

The first things to do (and not do) after a warning letter or platform complaint
How infringement is decided under Japanese law
Cases where a warning does not mean infringement
Your practical options and what the other side can do
What to prepare now, and how a Japanese patent attorney can help

First steps: don't admit, don't ignore, don't panic

When a warning letter arrives, three reactions cause the most trouble:

Admitting infringement immediately — an apology or admission in writing can later be used against you, including in a damages claim.
Ignoring the letter — if the claim is valid, silence can lead to a lawsuit, an injunction or a larger damages claim.
Replying emotionally — an angry reply rarely helps and may close the door to a settlement.

The right first step is to check the facts calmly: what right is being asserted, whether it is valid, and whether your use actually falls within it. Note any deadline stated in the letter, but do not let it rush you into a reply you have not checked.

Warning letters vs. Amazon Japan / Rakuten complaints

For cross-border e-commerce sellers, the "warning" often does not come as a letter but as a notice from the platform: a listing is removed or your account receives an "intellectual property complaint" filed by the rights holder.

If you received a platform complaint

Note the complaint details: the complainant's name, the trademark (and registration number, if given) and the listings concerned.
Check the cited registration in Japan's official database (J-PlatPat): is it registered, who owns it, and for which goods?
Platforms do not judge infringement the way a court does. A complaint can be wrong — for example, when you sell genuine products, or when the registration covers different goods.
Repeated complaints can affect your seller account, so respond through the platform's procedure (appeal, or asking the complainant to retract) rather than simply relisting.

Whether it is a letter or a platform complaint, the legal question is the same: does your use fall within the scope of the other party's Japanese trademark right?

What decides infringement in Japan?

In Japan, trademark rights are territorial and based on registration. As a rule, infringement requires both of the following:

Your mark is identical or similar to the registered mark, and
Your goods/services are identical or similar to the designated goods/services of the registration.

If either side is dissimilar, there is generally no infringement. Also note: a trademark you own in China, Korea, the US or elsewhere does not give you rights in Japan. What matters is the Japanese register.

Three things to check first

Checklist

1. The other party's registration: Is it actually registered in Japan (not merely applied for)? Is it still in force? Who is the owner? What exactly does the mark look like?
2. The designated goods/services: Which classes and goods does it cover? Are your products within them or similar to them?
3. How you use the mark: Is it your brand name on the product, packaging or listing title — or just a word in a product description?

A pending application cannot be enforced as a trademark right yet (although the applicant may later claim compensation after registration in some cases). The registration number allows us to check all of this quickly.

Should you stop using the mark immediately?

It depends. If the other party's registration is valid and your use clearly falls within it, continuing use increases your risk, and stopping (or pausing sales in Japan) while you negotiate may be wise. If there is a real argument for non-infringement, stopping immediately may cost you sales unnecessarily.

The decision should be based on the strength of the claim and the business impact — ideally after a Japanese patent attorney has reviewed the registration and your use.

A warning does not always mean infringement

Warning letters are sometimes sent even when the claim is weak. Common situations where there may be no infringement:

The marks look and sound different overall, or the goods are not similar.
You are reselling genuine products put on the market by the brand owner or with its consent (in general, reselling genuine goods is not infringement, although conditions apply, e.g. for parallel imports).
The word is used only to describe the product's quality, ingredients, use or compatibility, not as a brand.
The registration may itself be invalid, or the mark has not been used in Japan for 3+ consecutive years and is open to non-use cancellation.

Is it "use as a trademark"?

Japanese law focuses on whether a word or logo functions as a brand — identifying who the goods come from. Using a registered word merely as a descriptive term (for example, "compatible with XX" or a common ingredient name) may not be trademark use.

However, e-commerce sellers should be careful: putting another company's brand in your listing title or keywords to attract searches can be treated as trademark use and is also a frequent cause of platform complaints.

Your practical options

Option	When it fits
Argue non-infringement	The marks or goods are not similar, or your use is not trademark use. Reply in writing with reasons.
Modify or limit your use	Changing the name, logo or the products sold under it can settle the matter at lower cost than a dispute.
Stop use and negotiate	The claim is strong. Negotiate a transition period, a license, or even purchase of the registration.
Challenge their registration	The registration has grounds for invalidity, or the mark has not been used in Japan for 3+ years (non-use cancellation trial).

These options can be combined — for example, filing a non-use cancellation trial while negotiating.

What the rights holder can do

If the matter is not settled, a Japanese trademark owner can seek:

An injunction (stopping sales, removal of infringing goods)
Damages
Return of unjust enrichment
Measures to restore business reputation

Intentional infringement can also carry criminal penalties, and customs can stop infringing goods at the border. This is another reason not to ignore a well-founded claim.

What to prepare now

Collect the following before replying — it is the basis for any argument:

When you started using the name (in Japan and in your home country)
Which products or services it is used for
How it is displayed: logo, text, product listings, descriptions
Evidence: product photos, packaging, ads, websites, sales records
Any earlier contact with the other party, and the source of your goods (invoices, if you sell genuine products)

Also check whether you have your own Japanese trademark application or registration. If you do not, consider filing one for your brand (after confirming it does not conflict) so the same problem does not recur.

Why consult a Japanese patent attorney

Similarity of marks and goods is judged under Japanese examination and court practice, which can differ from your home country. A Japanese patent attorney can assess the registration, estimate the risk, draft the reply, and — if needed — file an invalidation or non-use cancellation trial at the JPO. If you have no address in Japan, any JPO procedure must in any case be filed through a representative in Japan.

At BrandAgent, every case is handled personally by a licensed patent attorney, and we communicate in English and Chinese. Consultations and quotes are free.

FAQ

Q. Does a warning letter mean we definitely infringe?
A. No. Infringement requires similar marks and similar goods/services, and use as a trademark. Warnings are sometimes sent on weak grounds.
Q. Can we just ignore it?
A. Not recommended. If the claim is valid, ignoring it can lead to a lawsuit or larger damages. Check the facts and reply in an appropriate way.
Q. Our Amazon Japan listing was removed. What should we do?
A. Check the cited Japanese registration on J-PlatPat and compare it with your product and listing. If the complaint is unfounded (e.g. genuine goods, dissimilar goods), respond through the platform's procedure or ask the complainant to retract.
Q. We own the trademark in China. Doesn't that protect us in Japan?
A. No. Trademark rights are territorial. Only a Japanese registration (or a Madrid registration designating Japan) gives rights in Japan.
Q. Do we have to stop selling immediately?
A. It depends on the strength of the claim. Have the registration and your use reviewed first, then decide.

Summary

Key points

Don't admit, ignore, or reply emotionally — check the facts first.
Infringement generally requires both a similar mark and similar goods/services.
Check the other party's Japanese registration, its goods, and how you use the mark.
Options: argue non-infringement, modify use, negotiate, or challenge their registration.
Protect your own brand in Japan with your own registration.

Received a warning letter or a platform complaint in Japan?
Send us the letter or complaint and the registration number — we will review it and reply with our view and a quote, free of charge.

BrandAgent Patent Office (Kyoto, Japan)
Toru Kano, Japanese Patent Attorney

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