Shares of Big Hit Entertainment more than doubled their Initial Public Offering (IPO) price on debut.  Big Hit is the management agency for BTS, the massively popular seven-member K-Pop group.

The debut is the biggest in three years on Korea’s Kospi exchange, and will make Big Hit’s Chief Executive a billionaire. The band members will also become multi-millionaires. It comes despite concerns the band will soon have to do military service.

Big Hit shares opened at 270,000 Korean won ($235; £180), giving the company a valuation of $8.38bn at the opening bell.

BTS is one of the world’s biggest acts, and many investors feel it’s a safe bet that they will continue to make money for Big Hit. Even in the age of digital streaming, their album sales are strong, and their shows sell out within minutes. They also have a large number of advertising partnerships for products ranging from cars to cosmetics. They recently had their first number one hit on the US Billboard charts.

Only 20 predominantly non-English tracks have ever cracked the Billboard top 10 in its 60-year history. Three of those are from BTS. Their first Billboard number one, Dynamite, was sung in English. Perhaps more significant in 2020 are their statistics on digital mediums. They were the number one act on Billboard’s Social Media fifty for more than 200 weeks.

In August, its single Dynamite became the first video to amass more than 100 million views in a day on YouTube. BTS is Big Hit’s biggest money maker by far, generating 88% of Big Hit’s revenues so far this year.

But some are worried that the company’s greatest strength is its greatest vulnerability.