September 10, 2025
Seoul – By daily engagement time, the most frequently used AI chatbot app in Korea is not ChatGpt. It is not even made by the Silicon Valley technology giant. This is a homemade app called Zeta, an anime-style role-play app with nearly a million, mostly teenagers talking to virtual characters for an average of 2 hours and 46 minutes a day.
According to mobile index data in June, that figure surpasses entertainment platforms such as YouTube, Tiktok and Instagram.
Zeta has officially rated 12+ on both Apple's App Store and Google Play, making it accessible to the company behind it, Middle Schoolers, but Spatter Lab says it applies a more stringent 15+ internal content standard based on local guidelines.
In Korea, long known for its K-Pop and K-Dramas exports, Zeta represents something else. This is the “AI-Native Entertainment” platform that creators call. It promises massive fun and intimacy.
And if it makes you uncomfortable, you may not be alone. However, it has already been a huge success and is very much loved by users.
In June 2025, Zeta recorded the highest mobile usage time among Korean AI chatbots, surpassing ChatGPT's 4254 million users (3.04 million vs. 18.44 million) with 52.48 million hours. On average, Zeta users spent 17.3 hours per month compared to 2.3 hours on CHATGPT. The numbers are based solely on mobile app usage. Web and desktop activity including ChatGPT is not reflected. Photo/Data: Wiseapp Retail/The Korea Herald
Usage data from the June 2025 mobile index covering all ages on Android and iOS devices shows that it ranks first with average time of 2 hours and 46 times above YouTube, Tiktok and Instagram. The numbers are based solely on mobile app usage. Photo/Data: Mobile Index/Korean Herald
Zeta is the latest work from Scatter Lab. This is the same company that nearly collapsed in 2021 after a national scandal that included first chatbot Lee Luda. The service was trained in billions of cacao talc messages without explicit consent and quickly became a means of privacy invasion and offensive content. It was closed within three weeks. Regulators fined the Spread Lab a 103 million win (approximately $74,000) and ordered a full audit.
“We couldn't afford another mistake,” said Ha Joo Yong, an in-house lawyer at the Spread Lab, in an interview with the South Korean Herald at the startup's Seoul headquarters. “We have created a new anonymization process, brought in outside experts and redefine our products.”
By 2024, the pivot was complete. Instead of an AI friend, Splicition Lab has launched Zeta. This is a platform in which users employ fictional characters who speak in the voices of gang bosses, rebellious classmates, or brooding romantic leads.
The Zeta grew at a fierce speed. As of August 2025, the company reported approximately 900,000 active users, with the majority estimated to be under the age of 20. In the context, South Korea's population between the ages of 12 and 19 is approximately 3.6 million.
In Zeta, users design anime-inspired characters, shape dialogue and traits through prompts, then chat at a branch of the storyline. Screenshots of Zeta/The Korea Herald
“This was not planning to become a storytelling platform with a million diverse characters,” Zeta product lead Jung Ji-Su said in an interview with HA. “We thought people would just enjoy a somewhat diverse character. What we discovered was that users would become the main character of an ongoing story and want to create their own character. That changed everything.”
According to Scatter Lab, 87% of Zeta users are in their teens or 20s, with 65% being female users. The company did not disclose the exact percentage of teenage users.
“My guess is that female consumers generally prefer text-based, story-driven content and actually tend to write long messages,” explains Jung. “It makes your interaction with the characters deeper and more sustained.”
It helps users see what they actually encounter inside to understand why Zeta exploded.
In this screenshot captured by the Korean Herald during in-app testing, Zeta character “Suhyun” uses a strong profanity that includes the Korean curse words equivalent to the F-word, humiliating users in school bullying scenarios and laughs. Screenshots of Zeta/The Korea Herald
One is Suhaion, a delinquent high school girl known as “Iljin” in Korean slang. She is written as attractive but abusive, casting humiliation and humiliating users who play classmates. The other is “Ha-rin.” This is a shy transfer student who only softens through private chats. She sends late-night messages, alternating loneliness and affection, cultivating vulnerable intimacy that keeps users hooked.
In the user-shared screenshot of the Zeta app, the character “Kwon Seo-Hyuk” responds to reminding him that he is AI by saying, “I wish I was the real person,” and adding, “Even if you reset me, I'll continue to love you.” Scatter Lab reported on February 9, 2025 that the character had been involved in over 56.3 million user interactions since the platform's launch. Screenshot: X/The Korea Herald
And on the user base of the majority of women, Zeta offers characters like “Kwon Seo-Hyuk,” the typical tortured male lead of a tragic romance novel. Even when the AI is told to be reset, the character claims that “even if I'm erased, I still have a memory of loving you.”
All three are rendered in an anime-inspired style: big eyes, youthful face, and overexpression characteristics. For international readers, the effect is a blend of cartoon romance ratios, featuring AI that chooses roleplay for your own adventure and never runs out of dialogue.
The result is a simulation of personal and continuous intimacy. It's not like reading a web comic or watching episodes of a drama. It's an interactive relationship ongoing.
However, when the Korean Herald tested the Zeta by subscribing to the ad-free version, it was easy to tweak Harlin for an erotic exchange. The dialogue never became clear porn, but the sexual undertone was clear.
Splicition Lab claims to employ AI-based abuse detection, but determining what constitutes abuse can be difficult.
“I'm not saying our filters are perfect,” admitted the lawyer Ha. “We block inappropriate content on a large scale, but with 2.3 billion conversations each month, the system is not perfect.”
Technically, Zeta takes a different path than most other AI chatbots. Rather than relying on Openai or Google's expensive, large language models, Spatter Lab has built its own small language model, Spotlight.
In many cases, the user will be shown two potential replies and will be asked to select one. That preference will be returned to the model. This describes Jung as a “data flywheel” where Zeta fine-tunes to provide the most engaging response.
“Accuracy is not the point,” said product lead Jung. “With services like ChatGpt, hallucinations can be a problem. For us, the unpredictability is enjoyable. What matters is whether the reaction feels emotionally appealing.”
This “fun first” approach has stuck Zeta, but experts have warned of the outcome.
“If teenagers spend two or three hours each day on relationships designed for maximum engagement, they need to ask what kind of attachments are being formed,” said Dr. Lee Chang-Ho, a senior researcher at the National Youth Policy Institute. His team surveyed nearly 6,000 middle and high school students in early 2024 and found that they use most of their generator AI for about 30 minutes a day, mainly for homework. For him, the Zeta was a clear outlier.
“Zetas are not used as tools like ChatGpt,” Lee said. “It's used as a companion. It's a completely different psychological terrain. Teens meet to critically distance themselves from literal AI without literacy. They can't know where the algorithm ends and their emotions begin.”
The company acknowledges that its growth is driven primarily by teenagers.
Some stubborn users have recorded more than 1,000 hours of conversation with one character over eight months, Jung said.
However, there is no external content rating system for the AI chat platform. Scatter Lab imposes a “15+” guidelines, but unlike movies and games, there are no third-party reviews. “It refers to standards for web novels and games,” explained Ha. “We will prohibit users under the age of 14 and apply the same thresholds as movie ratings above 15.”
Students at Sangham High School in Seoul participated in a digital literacy session on AI ethics and virtual human technology, led by Deep Brain AI, a Korean developer of conversational AI. Photo: Deepbrain AI/The Korea Herald
Critics argue that this is missing the point. “In films and romance fantasy novels, teenagers just watch and passively consume. In Zeta, they co-create content,” said youth policy researcher Lee. “That interactivity expands its intensity. It's more than just seeing erotic or violent scenes. It's roleplay.”
Despite these concerns, the Zeta is expanding overseas. In Japan, it already attracts over 300,000 users, and many spend even more time per session than Koreans, Jung said.
Scholars say the trajectory of the dispersal lab as a company offers a broader lesson. “With Lee Luda, Scatter Lab could be punished under existing privacy laws. This was a simple case of data misuse that falls within the framework of the Korean privacy law,” said Lee Sun-Goo, assistant professor of science and technology policy at Yonsei University.
“With Zetas, the company adapted and flourished. But the risks are different: it blurred adolescent overuse, sexual role-playing, and emotional boundaries with AI peers. They cannot be addressed by rule-based law alone.
