Sasaengpaen is a compound: sasaeng, a Sino-Korean term for private life, and paen, the Korean rendering of the English word fan. Usually shortened to sasaeng, it names a fan whose attention to a performer has become surveillance: someone who obtains the home address, acquires the unpublished schedule, books the adjacent aeroplane seat.
The specifics matter, because the term gets applied loosely to any fan who seems a bit much. In November 2024, The Korea Herald reported that IST Entertainment had found a GPS tracker fitted to a vehicle used by the boy band The Boyz, alongside repeated uninvited visits to the group’s agency, hair salons and home. A separate incident ended in an arrest on trespassing and assault charges.
Read against that arrangement, the sasaeng looks less like a malfunction of the K-pop fan relationship than like its most literal customer. The industry sells closeness. The sasaeng buys it, then goes and takes delivery.
This is not a defence, for reasons set out below. It is also a point about pricing rather than origins. Sasaeng behaviour is documented from the first-generation idol era of the late 1990s, roughly two decades before any of the subscription platforms existed. The impulse came first and the products arrived later, built to serve it.
What the platforms actually sell
Dear U’s bubble app launched in 2020. The Hollywood Reporter set out in October 2025 that subscriptions run at roughly four to five US dollars a month and are sold member by member rather than by group, and put the cost of following an eight or nine-piece at about thirty dollars a month. Bundle pricing on the app stores varies, so that figure is best treated as the magazine’s estimate rather than a tariff. Hybe’s Weverse runs a comparable service.
The design choices are the product. A broadcast is engineered to arrive as a text from one person to one person. Korea Economic Daily noted in 2021 that the bubble interface deliberately resembles KakaoTalk, the country’s dominant messaging app. Each message addresses the subscriber by a nickname the subscriber has chosen, and the app’s own store listing promises an anniversary date between fan and artist, and a message from the idol who calls your name.
The physical tier is built on the same principle. The Korea Times reported in January 2026 that album purchases operate as lottery entries for fansign events and video calls, with fans routinely buying dozens of copies, and sometimes more than a hundred, to improve their odds of a short conversation. Fandoms circulate the informal threshold, the number of albums it usually takes to be drawn.
Donald Horton and R. Richard Wohl described the underlying mechanism in the journal Psychiatry in 1956, writing about radio, television and film. They called it para-social interaction: an illusion of face-to-face exchange, cultivated on purpose by the performer, in which the audience is invited to respond the way an intimate would. They were describing a broadcasting technique, which Korean entertainment companies have since turned into a subscription with a per-member price.
The label does work for the people using it
J. Patrick Williams and Samantha Xiang Xin Ho published “Sasaengpaen” or K-pop Fan? in Deviant Behavior in 2016, drawing on interviews, participant observation and media analysis among K-pop fans in Singapore. Their subject is boundary maintenance. Fans who hired vans to follow idol groups from one public appearance to the next were adamant that they were not sasaengs, and built their own sense of legitimacy directly against the term.
This is one qualitative study, in a single city, with a small sample, and its fieldwork is now more than a decade old. It describes how a particular group of fans in Singapore talked about themselves, which is narrower than a claim about fandom in general. The useful part is the mechanism: the label marks a line that ordinary fans hold in order to stay on the respectable side of it.
The move predates K-pop by some distance. Joli Jensen argued in “Fandom as Pathology: The Consequences of Characterization,” her contribution to the 1992 collection The Adoring Audience, that characterising the fan as disturbed is what permits the rest of the audience to be characterised as normal. Her surname is misspelled as Jenson in the book itself, and the error has been copied through fan-studies bibliographies ever since.
Where prosecution begins
Some of this is straightforwardly criminal, and treating it as a cultural curiosity would be a mistake. In Korea Herald reporting from July 2025, three people including an employee of a foreign airline were referred to prosecutors over the acquisition and sale of celebrities’ flight booking details, among them BTS members. Police arrested the airline employee in February and two further suspects in March. Hybe monitored the social media accounts trading the data and submitted evidence.
Buyers have boarded the same flights, altered in-flight meal selections, and in some instances cancelled bookings or changed seat assignments.
That market needs a supply side as well as a demand side. What the buyer is purchasing is the thing the messaging apps advertise, minus the terms of service. Before the purchase is possible, someone inside an airline’s systems has to extract the booking data and a broker has to move it.
What this reading does not excuse
Explaining where a demand comes from leaves responsibility for individual conduct exactly where it was. The people who trespass and fit trackers are answerable for that, and Korean agencies have responded with legal action, blacklists and, at Hybe, a dedicated task force on the flight-data trade. Those are reasonable measures.
The harder question is about their limits. A company can prosecute the person who took an offer of closeness literally while continuing to sell the offer. In the accounts these sit in different columns, security under costs and the platform under revenue, and nothing requires the two to be read together.
The pattern is not confined to Seoul
The mechanics have generalised across the creator economy, in paid direct messages, tiered access, the streamer who reads your username aloud, the membership band that includes a monthly video call. K-pop industrialised them earliest and most thoroughly, which is why the vocabulary is Korean and why the failure cases surfaced there first.
Sell a relationship at scale, price the tiers by proximity, and a fraction of the customer base will conclude that a relationship is what they have bought.
Most will do nothing with that conclusion. A small number act on it, and are arrested, and the product does not change. So far no agency has been asked in public to account for the relationship between the two.
