MGS 2026 Recap: Viral Marketing in Japan Runs on Kaiwai
Have you ever taken a viral campaign that worked well in one market, launched it in Japan, and watched it quietly disappear? Korea and Japan look alike from the outside, but word of mouth spreads in almost opposite ways.
The daglo marketing team attended Modern Growth Stack (MGS) 2026, hosted by AB180 at the Westin Seoul Parnas from July 21 to 24, 2026. This recap covers "AI-Optimized Marketing Lessons from Viral Success in Japan," presented by Eunji Yoo of FreakOut, an ad tech company founded and publicly listed in Japan that now operates in more than ten countries. We transcribed it with daglo and pulled out what global marketers can use.
The key to viral marketing in Japan is kaiwai (界隈): tiny communities of people who share a specific hobby or interest. Tens of thousands of kaiwai are active in Japan today, and the place where you can see them most clearly is TikTok, with 42 million monthly users there.
Why an ad tech company is talking about viral marketing, and why Japan
AI ad tech has caught up across the industry so quickly that technology alone no longer sets anyone apart. FreakOut's diagnosis is that the remaining edge is what you say: a message that touches emotions so users choose to spread it themselves.
The session gave three reasons to look closely at Japan.
- It resembles Korea: Both have relatively isolated geography, languages of their own, and cultures where global trends don't transfer as-is. While most of the world uses Google, Korea leans on Naver and Japan on Yahoo! Japan, and instead of WhatsApp, people use KakaoTalk and LINE.
- High revenue potential: In mobile games, only the US, China, and Japan earn more than Korea, and Japan stands out on expected revenue per download. In one case, 3,000 Japanese users generated more revenue than 30,000 active Korean users.
- Easier to reach: Of the three, Japan is closest to Korea in population and land area. China is almost 100 times larger in area, and the US has 6.5 times the population.
How viral differs in Korea and Japan: time, empathy, and emotion
In Korea, virality runs on urgency: the sense that everyone is doing it and you're falling behind. In Japan, it runs on kaiwai, meaning empathy inside a small community. The session compared the two along three axes.
| Axis | Korea | Japan |
|---|---|---|
| Time | Everyone chases one peak, rising and falling together | Each community resonates on its own; depth and staying power matter |
| Empathy | Open, forum-style communities where users speak freely; communities keep growing | People follow trusted voices rather than voicing opinions; communities keep shrinking |
| Emotion | Competitive; whatever is new becomes the trend | Built around a familiar favorite; without a favorite to attach to, people don't follow |
Because Japanese communities keep shrinking, open space is hard to find. One place still worth exploring is web magazines, which are highly trusted within each category.
What is kaiwai? Japan's micro-communities, as seen on TikTok
Kaiwai originally meant a physical area, as in "the neighborhood around here." Today it refers to people who share a particular hobby or interest, and on social media it has become a meme in the form "the ___ kaiwai."
Some kaiwai, like people who "cancel" their daily bath, have even made the news, and one marketing platform ranks kaiwai trends every six months. These communities don't use forums and rarely state opinions, but their movements are easiest to see on TikTok. Here are the Japan TikTok figures shared in the session.
- One in three people in Japan uses it, with 42 million monthly users, roughly the population of South Korea.
- Users doubled in three years, around the same time the word kaiwai took off.
- TikTok Shop transactions grew 20 times in the four months after its Japan launch.
- 85.8% watch at least weekly, and 64% watch every day.
- More than 33% have visited a travel spot they saw in a video, and 29% have gone to see a movie in theaters after seeing it there.
How to run viral marketing in Japan: influencers and nano or micro tests
To reach a small community precisely, you need its shared language and context, and from overseas the best way to get that is through influencers. They are already trusted inside a kaiwai and know best how to make the content it loves.
FreakOut grouped common marketer problems into four and offered a fix for each.
| Problem | Approach |
|---|---|
| Can't find where the target audience is | Use existing data to identify communities around similar products, then list the authoritative creators that audience follows most |
| Don't know what to say | Continuously collect top posts in each community, classify them, and plan the first two seconds, titles, and search terms |
| Got a creator list but can't choose | Start with nano and micro creators, test reactions without overexposing the audience, then pick a direction |
| Can't tell if it's improving | Repeat analysis, execution, and review, and report organic and paid results side by side in numbers |
The session shared results too. On TikTok, the first eight videos in search results (the top 8) are decisive. A client that had zero videos there before the campaign took all eight afterward, which, combined with a Qoo10 Mega Wari sale, produced record revenue. A campaign with many nano and micro creators repeating one message grew in-store sales fivefold, and replanning videos with a creator who usually got about 200,000 views pushed two of them to 4 to 5 million.
Questions to ask before planning viral marketing in Japan
When technology is no longer a differentiator, the message is, and how a message lands differs by country. If you're preparing to enter Japan or run campaigns abroad, start with these questions.
- How you compare markets: Are you comparing expected revenue per user or per download, not just total market size?
- Separate messages: Have you planned urgency-driven messages and community-empathy messages separately for each market?
- Targeting unit: Are you defining audiences by interest communities rather than age and gender?
- Test order: Do you find a winning pattern with nano and micro creators before betting on big names?
- Channel assumptions: Are you judging TikTok by local usage data rather than your home-market experience?
For recordings where it matters who said what, like multi-speaker sessions or Q&A, daglo's Speaker ID is a useful feature. It remembers the voices of the people in your recordings and fills in their real names instead of "Speaker 1" from the next recording on, and daglo is the first service in Korea to offer it to every user. Learn more about Speaker ID
For the other sessions we attended, see our full MGS 2026 recap. Event details are on the official MGS 2026 site.
#MGS2026 #ModernGrowthStack #FreakOut #JapanMarketing #ViralMarketing #Kaiwai #TikTokMarketing #daglo
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