How to Do Keyword Research for Amazon Japan

Creating a listing for Amazon Japan is easy. Get someone to translate your content, upload it, and you are live. But if you want to actually succeed in Japan, you need to understand something fundamental: Japanese uses four different writing scripts, and shoppers search using all of them.

This is not a complication. It is an opportunity. While your English listing competes on one set of keywords, your Japanese listing can capture traffic from four different variations of the same search term. You have four times the opportunity, but only if you do the research correctly.

Why Japanese Keyword Research Is Different

Two things make Japanese fundamentally different from English for Amazon optimization:

No spaces between words. Japanese text runs continuously. Where English clearly separates "kids mask" into two words, Japanese runs characters together. Only someone who understands the language knows where one word ends and another begins. This affects how Amazon's algorithm parses and matches keywords.

Four writing scripts. Japanese people mix and match four different scripts in everyday use. The same word can be written multiple ways, and shoppers search using whichever version comes to mind. If you only optimize for one, you miss the others.

The Four Scripts You Need to Know

Here is how to identify them: Hiragana characters are curvy and flowing. Katakana characters are sharp and angular. Kanji characters are complex pictographs with multiple strokes. Romaji is the English alphabet you already know.

Real Example: Kids Mask

Let's see how this works with a real product. "Kids mask" can be written four different ways in Japanese, and each version has different search volume.

The Kanji version (子供マスク) has the lowest search frequency rank, meaning it is the most popular. That version should be in your title, as close to the front as possible. The other versions should be in your bullet points, backend keywords, and PPC campaigns.

If you only optimized for one version, you would miss three other streams of traffic. This is why Japanese keyword research requires 4x the effort of English, but also offers 4x the opportunity.

The Research Process

The Hiragana Trap

There is a critical warning about Hiragana that most sellers learn the hard way.

This happens because Japanese has no spaces. The algorithm cannot reliably determine word boundaries with Hiragana, so it tries different combinations. Katakana does not have this problem because it is reserved for foreign words, and the algorithm handles it differently.

If you see strange search terms in your reports, keywords that seem completely unrelated to your product, check if they are Hiragana rearrangements. The fix is switching from Broad Match to Phrase Match.

PPC Strategy for Japan

Script Type	Match Type	Notes
Katakana	Broad, Phrase, or Exact	Safe for all match types. Foreign words are handled cleanly.
Kanji	Phrase or Exact	Complex characters. Phrase match is generally safe.
Hiragana	Phrase or Exact Only	Never use Broad match. Character rearrangement causes garbage matches.
Romaji/English	Broad, Phrase, or Exact	Behaves like standard English keywords.

Best Practices Summary

1. Research all four scripts. Every seed keyword needs Hiragana, Katakana, Kanji (where applicable), and Romaji variations.
2. Prioritize by search frequency. Use Brand Analytics to find the most popular version. That goes in your title.
3. Avoid Broad Match for Hiragana. The character rearrangement problem will waste your ad spend.
4. Include English keywords. Japanese shoppers search in English, especially for foreign products and brand names.
5. Keep campaigns small. No more than 10 keywords per campaign. Budget distributes evenly, and data stays clean.
6. Use Auto campaigns for discovery. When you do not know the language, let Amazon's algorithm find keywords for you. Harvest winners into manual campaigns.
7. Verify everything twice. English to Japanese, then Japanese back to English. Similar-sounding words can mean completely different things.

Working with Translators

If you just hand your English listing to a translator, you will get a grammatically correct translation that is not optimized for Amazon. The translation might read beautifully but miss the keywords that actually drive traffic.

Before translation, do your keyword research. Identify the most popular script variations for your main keywords. Then tell your translator: "I need these specific keywords included, in this priority order, using these exact scripts."

A good translator will integrate the keywords naturally. But they cannot do keyword research for you. That is a separate skill set that requires understanding Amazon's algorithm, Brand Analytics, and search behavior.

The Bottom Line

Amazon Japan is not a translation project. It is a market entry that requires understanding how Japanese shoppers search. The four-script system that seems like a complication is actually your competitive advantage, if you do the research.

Most sellers skip this work. They translate their listing, set up a few auto campaigns, and wonder why Japan does not perform. The sellers who succeed are the ones who research all four script variations, structure their PPC correctly, and optimize their listings for how Japanese customers actually search.

At PPC Ninja, we have native Japanese team members and years of experience with Japan expansion. We offer Japanese keyword research, title optimization, competitor analysis, and campaign setup services specifically designed for brands entering or scaling in Amazon Japan.