Japan SEO: How Many Compound Nouns Does Your Industry Need?

KIJI-SEO analyzed 4,152 Japanese compound nouns across 400+ domains to answer a question agencies couldn't: what does optimized Japanese content actually look like? The result is industry-specific benchmarks for Japanese SEO - taken from top 10 SERP positions across 152 classified keywords.

1. Why Agencies Can't Answer "Are We Optimized?"

Every agency hears it: "Are we doing enough?"

For Japanese SEO, there's never been a good answer. Traffic reports show visits. Rank trackers show positions. But nothing shows whether your content strategy matches what your industry actually needs.

The problem starts with language. Japanese uses three writing systems — kanji, hiragana, and katakana — often mixed in the same sentence. This creates compound nouns that Western SEO tools simply miss.

Tools like Ahrefs and SEMrush can process Japanese text. But as WPIC's Japanese SEO guide notes, "they don't fully grasp its nuances." The result? Agencies guess. Clients wonder. And 41% of SEO campaigns fail to prove ROI within the first year.

What's missing is simple: industry-specific benchmarks for Japanese compound noun optimization.

Until now.

2. What Are Japanese Compound Nouns (And Why Do They Matter)?

Japanese compound nouns are words made by joining two or more smaller words. In English, think "toothbrush" or "laptop." In Japanese, these compounds are everywhere — and they drive search behavior.

Examples of Japanese compound nouns:

Notice the last example. It blends kanji (観光) with katakana (スポット). This mixing of Japanese writing systems is common — and it's where Western SEO tools struggle.

2.1. Why Compound Nouns Dominate Japanese Search

Japanese doesn't use spaces between words. A phrase like 京都観光おすすめスポット (recommended Kyoto sightseeing spots) appears as one unbroken string. Search engines must break this into useful units. The compounds inside — 京都観光, おすすめスポット — carry the real search intent.

Research on Japanese keyword behavior shows that users search differently than English speakers. They often type full compound phrases rather than single words. A user searching for investment advice won't type 投資 (investment) alone. They'll type 資産運用方法 (asset management methods) or 初心者向け投資 (investment for beginners).

2.2. The Problem for Japanese Language and Western SEO Tools

Tools like Ahrefs and SEMrush use basic text analysis to break Japanese into words. But Japanese compound nouns need deeper processing — knowing which word pairs form real search terms.

The result: Western tools report single-word keywords but miss the compound phrases that Japanese users actually search. An SEO report might show 投資 appears 15 times. But it won't show that rivals use 不動産投資, 資産運用, and 長期投資 — three different compounds with three different search intents.

2.3. Why Compound Noun Optimization Matters in Japanese SEO

• Longtail keywords in Japanese are usually compound nouns
• Matching user intent requires the right compounds, not just root words
• Rivals ranking above you likely use compounds you're missing

Without compound noun analysis, Japanese SEO is incomplete. You're optimizing for words — but users search in phrases.

So how many compound nouns does your content actually need? The answer depends on your industry.

3. Compound Noun Density by Industry (The Data)

We analyzed 4,152 Japanese compound nouns across 400+ domains in 12 industries. The data comes from top 10 SERP positions across 152 classified keywords. The question: how many compound keywords appear per domain in top-ranking content?

The gap was massive.

That's an 18x difference between Manufacturing and Education.

Generic Japanese SEO advice fails because it ignores this gap. A Travel site targeting 69 compounds is wasting budget. A Manufacturing site with only 20 is losing to rivals.

The first question for any Japanese SEO strategy: What's the benchmark for your industry?

4. Kanji, Hiragana, or Katakana? Industry Patterns

Japanese compound nouns aren't just about quantity. The script mix matters too.

Our data shows clear industry patterns:

4.1. Kanji-Heavy Industries (45-52% Pure Kanji Compounds)

• Health & Medical (52%)
• Real Estate (49%)
• Legal & Business (45%)

These industries signal authority through kanji. Technical terms, formal language, and set phrases dominate. Content that leans too casual — too much hiragana — feels cheap to Japanese readers.

4.2. Katakana-Blend Industries (42-45% Kanji + Katakana Hybrids)

• Sports & Outdoor (45%)
• Retail & E-commerce (43%)
• Technology (42%)

These industries absorb foreign loanwords. Terms like サステナブルツーリズム (sustainable tourism) or ランチ営業 (lunch service) blend katakana with kanji naturally.

4.3. Getting Japanese Longtail Keyword Balance Right

If your Legal content uses too much katakana, it may feel foreign to Japanese searchers. If your Tech content avoids katakana entirely, it misses how the industry actually speaks.

Match your script balance to your industry. Your content will feel native — not translated.

KIJI-SEO provides automated compound noun detection and industry benchmarking for agencies targeting the Japanese market.

5. Longtail Keywords: Too Few or Too Many?

Both problems cost money.

Under-optimized content:

• Misses Japanese longtail keywords your competition use
• Fails to match search intent
• Loses rankings to more complete content

Over-optimized content:

• Stuffs keywords that don't boost rankings
• Wastes writing budget on shrinking returns
• Can trigger quality penalties from unnatural density

How to check your situation:

1. Check your compound count. How many unique compound nouns appear in your top pages? Compare to your industry benchmark above.
2. Check your script balance. What share of your compounds are kanji-only vs katakana blends? Does it match industry norms?
3. Check rival gaps. Which high-use compounds appear in top-ranking rivals but not in your content?

If you're below benchmark: focus on adding missing compound nouns.

If you're above benchmark: check for keyword stuffing or off-topic terms.

If you match the benchmark but still lag: the problem isn't quantity — look at content quality, structure, or backlinks.

6. Using These Benchmarks in Client Reports

For agencies serving the Japanese market, these benchmarks solve a real problem: proving your content strategy is right.

Before these benchmarks:

"We've optimized your content for Japanese search." Client: "How do you know it's enough?" "...trust us."

With industry benchmarks:

"Your Manufacturing content uses 28 compound nouns per page. The industry benchmark is 69. Here's the gap analysis and our plan to close it."

How to apply this in reports:

1. Audit current compound density — Count unique compound nouns in your client's top 10 pages.
2. Compare to industry benchmark — Show where they stand vs. the data.
3. Find specific gaps — Which high-value compound nouns are missing?
4. Set clear targets — "Increase compound density from 28 to 55 over 6 months."
5. Track progress monthly — Show movement toward the benchmark.

This turns Japanese SEO from guesswork into a clear strategy. Clients see exactly where they stand. Agencies prove their value with data.

7. The Bottom Line

Japanese SEO has run without content-level benchmarks — until now.

The data is clear:

• Compound noun density varies 18x across industries
• Script mix (kanji vs katakana) follows industry patterns
• Generic optimization advice fails because industries differ

For agencies and businesses targeting Japan: know your number. Benchmark your content. Stop guessing whether you've done enough.


This analysis is based on 4,152 Japanese compound nouns across 400+ domains. Industry benchmarks derived from top 10 SERP positions across 152 classified keywords.


KIJI-SEO provides Japanese compound noun analysis and industry benchmarking for agencies and businesses entering the Japanese market.