Several months ago, I was in Los Angeles covering a Korean pop show for a major magazine. They ended up killing the story, considering K-pop “too niche” for their readers; somehow, this felt both totally accurate and maddeningly myopic. K-pop remains a largely underground movement in the States, mostly the ken of geeky music journalists, Asian Americans, and gays weary of Lady Gaga’s art-pop pretensions but thirsty for a similar spectacle. And yet, K-pop seems perpetually on the verge of breaking into the mainstream in a meaningful way: The Wonder Girls toured with the Jonas Brothers; Girls’ Generation performed on Letterman a few months ago; and 2NE1 were signed by execrable hip-pop monster will.i.am’s management company after he promised to make them a global sensation. Most recently, Psy’s video for “Gangnam Style” made him a viral phenomenon overnight; his appearance at the VMAs last Thursday night gave K-pop its broadest exposure yet, albeit still more as a novelty act than for its musical merits.

The festival I attended, SM Town 2012, featured several of the biggest acts signed to the monolithic Korean record label SM Entertainment. SM’s top-performing girl group, Girls’ Generation, is my favorite, but that day the fans were showing up for the boy bands: Super Junior, SHINee, and EXO. The mood at the concert was crazed. These acts, who sell out arenas across Asia and are ubiquitous on variety shows and in magazines overseas, tour in the United States infrequently. The druggy anticipation of their performance hung as thick over the crowd as a fever.

At the press conference before the show, representatives from each group (most of the acts performing were girl groups or boy bands, some topping out with as many as 12 members) gave answers to preselected questions from journalists, which were translated from Korean by a breathless interpreter. On a stage, well-lit and costumed, they looked cartoonishly tall and glamorous. I found myself particularly taken with one chisel-jawed singer, half of the vocal duo TVXQ, whose sexual energy radiated from the stage.

I tweeted, joking: “Who is this guy from TVXQ and why does he keep undressing me with his eyes?” A few moments later, my timeline was flooded with responses from the few dozen K-pop fans who followed me, as one of the handful of American music journalists who had jumped on the K-pop bandwagon; they identified him as Yunho. I quickly followed up: “Turns out his name is Yunho and we’re eloping after the concert tonight, bye.” Those tweets were retweeted in rapid-fire succession, and soon my phone was vibrating with so many new followers that I had to turn off my notifications. The following morning, emboldened by the viral success of those tweets, my rising follower count, and the sheer fact that this all seemed incredibly funny, I wrote: “Would it be annoying if I began tweeting snippets of erotic fan fiction about this K-pop artist named Yunho who stole my heart last night?” I tried one out: “His cheekbones were haughty, even regal, but his eyes were warm as Yunho pressed his hand against my chest. ‘You belong to me,’ he said.” Then another: “His lean form silhouetted in moonlight, Yunho gazed wistfully toward the cresting waves. ‘Sam,’ he whispered. ‘Our love is special.’” For context, I clarified: “These tweets are excerpted from my forthcoming work of fiction, ‘Fifty Shades of Yunho.’”

Several of my new followers pointed me to the handle of another K-pop star, Kim Jaejoong, from the boy band JYJ; it wasn’t hard to figure out that the fans believed that Yunho and Jaejoong were gay lovers. I was on a trolling high. Foolishly, I tweeted at him. “@mjjeje Hey, guess what? I’m coming for your man. Hope you’ve got him on a tight leash.” Overnight, my followers skyrocketed; I received friend requests from dozens of Asian K-pop fans; GIFs and memes were made using my Twitter photo; someone on Tumblr took a screenshot of that string of tweets, which has 1,178 notes to date. A month later, I was sent the scan of a Japanese tabloid called Yoochun News, which had an article about the mysterious American journalist (I was identified in silhouette only as Mr. S) whose love for Yunho had captivated fans.

Most chillingly, though, there was a deluge of death threats from crazed fans who, whether they perceived me as an actual threat to the imagined romance between Yunho and Jaejoong or merely an annoyance who should to be silenced, gave me pause in an online game that had become addictively pleasurable. “Let me show you how you shall die,” one began. “@mjjeje has only a 100+ stalkers. One order from his lush lips … and your throat shall be slit!” There were many others, but that one stuck with me — mostly because it was retweeted so many times.

Korean pop is an inherently surreal and dazzling form of music, so it makes sense that the culture that surrounds it would be equally surreal and dazzling. K-pop songs — at least the ones by my favorite acts, groups like Girls’ Generation, 2NE1, and Super Junior — often sound like they were manufactured from a dozen different songs in some futuristic pop laboratory, Frankenhits comprised of gleaming little hooks and riffs, breakneck pastiches that range from twee synths to muscular nu-metal but remain grounded in a firm melodic sensibility that transcends language barriers (so you can sing along without knowing Korean, which is useful for whatever-the-Korean-equivalent-of-a-gringo-is types like me).

It’s as much a visual style as a sonic one, though, and the videos are where the magic happens. Like American pop stars, K-pop “idols” — as they’re known — are uniformly willowy, beautiful, and charismatic, with jaw-dropping choreography and dizzyingly high production values. Unlike American pop stars, K-pop idols command a level of obsession among their fans that easily outshines the Beliebers and Directioners, and their choirs of screaming adulation have become as much a part of an album campaign as the music itself. No, K-pop fans can be scary.

“K-pop is like a drug,” an executive at a top Korean label told me. (He asked to remain anonymous.) “The fans — they’re hooked. It’s like a cult, or a drug that they want more and more of.”

The cultish devotion to pop stars isn’t geographically or culturally restricted; “stans” is the nifty neologism for crazed fans that’s both a portmanteau of “stalker” and “fan” and an homage to the 2002 Eminem single, whose eponymous antihero’s obsession with the rapper drove him to suicide. (Stan culture even garnered a trend piece in the New York Times last year.) Stans are prone to hyperbole and extremism: In stan parlance, the chart success of Britney Spears (or, the likelier moniker, Godney) means she’s rendering all of your faves irrelevant, while the commercial underperformance of Keri Hilson’s last album means she’s fated to live out her days mopping the floors at a Decatur Walmart. But among fans of mainstream American artists, stan culture is primarily limited to the annals of forums, Tumblr, and Twitter; then there are occasional outliers, like Directioners who hide on a tour buses or middle-aged men who show up at the homes of Disney triple threats.

That’s a fairly predictable, if often lamentable, symptom of a culture driven by celebrity obsession, but the Mark David Chapmans of the American pop universe tend to be anomalous. With K-pop, stan behavior carries over into the real world with frequent, alarming consequences. In my estimation, the most majestically insane instance of this surrounded the object of my affection, Yunho, who was backstage during the taping of a variety show several years ago when the fan of a rival group sneaked backstage and poisoned him. (Yunho was hospitalized and the perpetrator was arrested.) Perhaps this augured the era of the sasaeng fan, a recently coined term that might as well be Korean for “stan”: “Sa” means private and “saeng” means life, in reference to fans’ all-encompassing obsessions with their preferred artists.

A recent Korean news segment about sasaeng fans suggests that Yunho’s poisoning was far from an isolated incident, although it’s as dubiously hysterical as a Nancy Grace special report. (The English subtitles are serviceable, if clumsy: “Right now is the golden age of idols in Korea and fans make them shine brighter!”) There’s footage of girls sprinting in pursuit of cars carrying K-pop stars down the rainy streets of Seoul and a fuzzy clip of one boy-bander slapping a crazed sasaeng fan. (He calls the experience “immensely terrifying.”) One girl, interviewed from the neck down to protect her identity, claims that saesang fans skip school to stalk K-pop artists, secretly install CCTV cameras in their homes, hack their mobile phones, steal their underwear, and leave used tampons on their doorsteps. (Ugh.) According to the segment, sasaeng fans hire special taxis to chase K-pop idols; due to the prohibitively expensive cost of trailing them all day via taxi, some girls have resorted to prostitution. (This is where the segment, which already strained credulity, lost me, although it’s a thrillingly tawdry notion: Teenage Korean girls selling their bodies to stalk celebrities? The Beliebers could never.)

The term “idol” correlates with the tendency toward celebrity apotheosis worldwide, but in the States, it’s rare to find anyone other than Ryan Seacrest use it to describe a pop star, since I don’t know that American fans care as much about idolatry so much as they care about themselves. Consider the instances of stalking, hacking, and B&Es targeting celebrities in the Western world: the Hollywood Bling Ring started with Alexis Neiers’s unquenchable thirst for Marc Jacobs accessories; stalking is the domain of paparazzi spurred on by the high market value of a photo of Blue Ivy to the tabloids; and hacking is nearly synonymous with Rupert Murdoch and The News of the World’s efforts to sell more papers by any means necessary. All of these aims are ultimately selfish ones, crassly commercial or materialistic. For the sasaeng fans, the business of deifying K-pop stars serves no indirect function: The lawless obsession isn’t a means to an end, it’s an end itself.

That type of devotion is an A&R dream, and manufacturing fan support of that ilk should be a good thing, so it’s easy to see K-Pop fandom as a runaway train; the label executive I spoke with insisted that the fan engagement was organic but difficult to rein in. “There are no masterminds at our companies,” he said. “It happens itself. These fans create groups themselves, and find members. You can do it so easily now, with the technology of the Internet. It’s a lot more accessible. It’s just a cult … It’s really hard to control.” Perhaps the runaway train of K-pop fandom, in its en masse furor, is a testament to some fundamental difference between Eastern and Western cultures, although I doubt it can be reduced to as simple a dichotomy as collectivism vs. capitalism. The music industry is still a business, after all. Still, when I interviewed two members of Girls’ Generation (who spoke in confident, if demure, English) before their performance at SM Town, it seemed significant that both tended to use the first-person plural pronoun when they answered my questions. “We’re so proud to be representing Korea here,” and so on.

Regardless of the cause, the mass hysteria (or calculated insanity, who knows?) of the sasaeng fans indicates that the Hallyu wave is swelling to a tsunami. Psy is currently perched at the crest: Ironic, after all the time and money that has been spent attempting to launch K-pop girl groups here. Whether his viral success will translate into longevity remains uncertain, but a recent high-profile signing by Justin Bieber’s manager Scooter Braun seems about as good a vote of support as a Korean superstar could want. And as for Mr. S? I’m trying not to tweet anything inflammatory about Yunho anymore, if only to not drown in the tide.

Sam Lansky is a writer from New York City. He writes about entertainment and culture for New York Magazine, The Atlantic, and MTV Buzzworthy.