Expanding to Japan and Korea: an ASO playbook
Japan and Korea are two of the most lucrative mobile markets per user globally. They're also two of the markets where US-centric ASO breaks down hardest. The keyword patterns, screenshot conventions, and discovery behaviors are different enough that "translate the description and ship it" produces measurable failure.
Here's the practical checklist.
Step 1: Localize the screenshot captions FIRST
Before you translate the description, before you research keywords, before you commission UI translation — translate the captions on your screenshots.
Reason: as covered in the screenshot conversion rules post, captions drive ~half the install decision. A translated caption over an English UI dramatically outperforms an English caption over a localized UI in non-English markets.
Use a native speaker, not Google Translate. Marketing copy doesn't survive machine translation in either Japanese or Korean.
Step 2: Research keywords in the local language separately
The intuition trap: assume your top US keyword translated to Japanese is also the top Japanese keyword. It often isn't. Search volumes, competitor density, and even synonym preferences vary substantially.
Examples:
- "Meal planner" in Japan → "献立アプリ" (kondate app) is much higher volume than the literal translation "ミールプランナー".
- "Workout tracker" in Korea → "운동 기록" (exercise record) is more common than the loanword "워크아웃 트래커".
Use a tool that provides per-storefront keyword volume. Research as if you're starting fresh in that market.
Step 3: Take advantage of the keyword field separation (Apple)
Apple lets you set a different 100-character keyword field per storefront. Use it. Your Japan keyword field should be packed with Japanese terms, not transliterations of English. Same for Korea.
A common mistake: copy-pasting the US keyword field into all storefronts. You're wasting 100 characters of free indexing per market.
Step 4: Watch for length issues in the subtitle
Japanese and Korean characters carry more semantic weight per character. Apple's 30-character subtitle limit means a Japanese subtitle can fit much more meaning than an English one. Use this — pack the subtitle with high-weight terms.
Korean follows similar density rules. The English-language pattern of "Verb your noun in adverb manner" doesn't apply; Korean and Japanese sentence structure differs enough that the structures from the subtitle patterns post need adapting.
Step 5: Account for review-rating culture differences
Japanese users rate apps lower on average than US users. A 4.0 rating in Japan corresponds roughly to a 4.4-4.5 rating in the US. Don't panic at numbers that look low compared to your US baseline. Compare against Japan-specific category benchmarks.
Korean users skew higher and review more frequently than US users — getting to 1,000 reviews in Korea often happens faster than in the US for the same install volume.
Step 6: Don't auto-translate review responses
If you're responding to reviews (you should be), use a native speaker or skip responding in markets where you can't. Auto-translated responses are recognizable and hurt brand perception more than not responding.
Step 7: Measure rank distribution, not just position
Both markets have very different competitor density. Top 10 in a niche US category might mean top 100 in a hyper-competitive Japan equivalent. Track the distribution of your tracked keywords across rank bands (Top 1, 2-5, 6-10, 11-30, 31-100, 100+) over time — that's the better health metric than any single rank.
When to expand
Tactical advice: don't expand to Japan or Korea before you've validated product-market fit in your home market AND you have someone (employee or contractor) capable of native-language customer support. The localization investment is meaningful enough that pre-PMF expansion usually doesn't pay back.
Rank Sonar tracks rank, ratings, and metadata across all 15 storefronts on every tier. [Try it free for 14 days](/pricing).