It is hard to know which was more surprising as I sat in my parents' living room on a visit to Britain in May: that the South Korean boy band BTS were guesting on the flagship television show "Britain's Got Talent" or that my parents already knew who they were.
Two days after that appearance, BTS appeared in front of 70,000 fans at London's Wembley Stadium -- another milestone in an impressive rise to the top.
K-pop broke out of South Korea years ago. I first witnessed this while reporting on sport elsewhere in Asia. In the buildup to soccer games in Thailand, I could hear South Korean music blaring from the loudspeakers. On top of that, the ambition of my daughter's Malaysian friend was to be a K-pop star. Less pleasantly, I was the subject of abusive messages for weeks from Vietnamese and Chinese fans of a K-pop group I mentioned in passing on social media.
Many predicted that the bubble would burst, and that even the most successful groups would quickly suffer the same international eclipse as Psy (real name Park Jae-sang), who had a one-off global hit in 2012 with "Gangnam Style." However, groups such as BTS and Blackpink -- currently in the middle of a 36-date tour of the world's big arenas -- are going from strength to strength. Indeed, the only threat on the horizon for BTS is likely to be military conscription -- all South Korean males must serve about 20 months before they are 30.
There are lessons to be learned from Psy. His catchy song and mesmerizing video were viewed more than 1 billion times on YouTube. That would be an impressive feat now, but in 2012 it was something else. Psy, a long-time star in South Korea, quickly faded from international view. He did not make as much use of social media as the new bands do. Social media has played a major part in the marketing and packaging of his more polished successors. Sites such as Facebook, Twitter, Instagram and YouTube allow BTS, Blackpink and others to communicate directly with fans in various languages, as traditional barriers to international cultural exchanges soften.
At the start of the 21st century, traditional media in Western countries would have been highly unlikely to take any notice of an Asian boy band, especially one that sang primarily in Korean. But social media allows bands like BTS to access millions of fans before they arrive in a country, generating demand for stadium shows, popular TV chat appearances and talent extravaganzas. Culturally, much of the world enjoys the same TV shows, movies and music, albeit largely in English.
Modern technology makes life easier for South Korean bands, but attaining international success still requires a lot of work. Like most K-pop bands, BTS sing in Korean with a liberal sprinkling of English, especially in choruses, which tend to be repetitive and simple to follow. The videos that go with the songs are often shiny, busy and entertaining, with a focus on synchronized dancing. Concerts are even more spectacular, with tens of thousands of fans waving light sticks in time to the music and trying to follow the lightning-quick footsteps of their idols.
Not long ago, Japan was the preeminent musical power in Asia. There is no general consensus on the similarities between the pop scenes in the two countries, but there is no doubt that Japanese bands have fallen far behind their South Korean rivals internationally -- perhaps because of the relative size of the two music markets.
With almost three times the domestic audience of South Korea, Japanese groups that make it big at home can make more money than their K-pop counterparts, encouraging a more international outlook among their South Korean rivals. South Korea has also been much more aggressive than Japan in seeking overseas markets for cultural exports as part of a government-backed hallyu (Korean wave) movement that also includes television and movies. Some K-pop bands have members who can speak English, Chinese or Japanese, and some recruit members from overseas for this very reason.
"K-pop is easier to follow," said Sophia Ong, a music fan in Malaysia, told me. "I quite like J-pop, but it's hard if you don't speak the language, and it can be a little too 'cute'. Korean bands are more international and are more fun."
It seems, though, that fun is a serious business. K-pop is an unforgiving and competitive industry, seen at home as a product to be exported. The product is systematic and slick, but behind the scenes a lot of work is needed to get bands like BTS into the world's living rooms.
John Duerden is a Seoul-based journalist.