The bust of a routine scam on a popular secondhand marketplace platform in Cheonan, South Chungcheong Province has led to the additional arrest of a previous unlawful user of cannabis, and uncovered in the process a complex web of illegal activity.

On March 9, a fraud report was first made at Cheonan's Seobuk Police Station. In the report, a buyer claimed they were defrauded after trying to purchase vouchers for Seoul Pay — a mobile payment service run by the Seoul Metropolitan Government — on Karrot, an local online platform for trading secondhand items operated by Danggeun Market Inc.

The buyer had sent 180,000 won ($140) to the seller, who promptly vanished. Initially dismissed as a simple fraud case, it was later discovered that an individual wanted for previous illegal cannabis use was behind the crime. Recreational use of cannabis is illegal in Korea.

Initial investigations by the police officer in charge led to the discovery that the seller had two distinct identities: one as the owner of the phone and another as the owner of the platform account. However, the phone was registered to a frequent scammer while the account was tied to the known unlawful cannabis user.

This clue alerted the officer that the situation was more complex than a typical secondhand marketplace scam.

By examining the drug suspect's bank account transactions, she was able to identify places frequented by the account owner. This further revealed that he was operating a PC bang -- a type of gaming room and internet cafe -- illegally.

This information prompted an undercover operation at the PC bang, which led to the appearance, positive drug test and arrest of the account holder on April 21.

As the case unraveled, it became clear that the owner of the phone, who had accumulated debt at the PC bang, had been attempting to clear the debt by fraudulently selling the Seoul Pay vouchers. Neither individual had been aware of the other's identity.

Innocent buyers of the fake Seoul Pay vouchers posted by the phone owner would end up falling into the trap of paying for them by sending money to the account owner, ultimately amounting to an elaborate scheme to pay off the phone owner's debt to the PC bang.

Now both individuals face charges, with the phone owner accused of fraud and the account owner facing charges for illegally using cannabis and running the PC bang.

Although Seobuk Police Station in Cheonan deals with around 200 secondhand marketplace scams a month, it is rare to uncover a crime related to illegal drug use in the process, according to the investigating officer in charge.