• Seventeen's new album has been fueling a K-pop photo card trading frenzy. • The variety of photo cards has spawned a booming market for trading and collecting. • The cards' popularity come as K-pop companies' stock soars.

"I have your man," I typed at 1 a.m., my hands trembling with excitement. "Do you have Joshua on hand to trade?"

Joshua Hong's K-pop band Seventeen released a new album on May 26. That album comes with serious math for trading card aficionados: There are seven versions of the record, each containing four photo cards — that's 336 unique cards, or "boy paper," to collect. I wanted him badly enough to wheel and deal my way through a maelstrom of trading card listings.

My late-night obsession is a small sliver of the sprawling business of K-pop photo card trading, a

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