Singer Kim Jae-joong in his latest Instagram post on Monday, one day after holding a fan concert, criticized "sasaeng taxis" that move fans around to facilitate their stalking.

Sasaeng is a K-pop slang term referring to hardcore fans who stalk artists.

Kim sarcastically wrote on his Instagram post that it's not surprising to see people, meaning taxi drivers, making money off of engaging in such mission-impossible-like missions.

"Sasaeng taxis waiting outside on every corner; Drivers who say they have no choice but to chase after [the car carrying celebrities] as their customers request it,” the singer wrote in his Instagram story Monday, alongside a clip of such taxis.

The clip showed taxis standing waiting outside the venue of the singer's fan concert, which ended on Sunday at the Blue Square in Yongsan District, central Seoul.

“However, times have changed. I secured the Blackbox footage of six vehicles, and I am planning to collect more in the future,” he added. “I hope those who violate another's privacy and cause suffering receive a severe punishment."

“I still remember the frightening words of someone saying, ‘I’m going to go to your wedding when you get married,’” Kim said. “I hope that the person keeps their promise so they can serve jail time.”

“[It’s been] 20 years. Let’s end it here.”

The singer also revealed the taxi’s business card, adding that “the taxi operators are more evil than the passengers who use the taxis,” saying that the drivers pass on the responsibility to their customers, blaming them, even though it's the drivers who are making money and breaking the laws.

Kim debuted in 2003 as a member of boy band TVXQ. He left the group along with members Kim Jun-su and Park Yoo-chun, and the three formed the boy band JYJ in 2009. As a solo artist, Kim is known for his hit songs like "Mine" (2013) and "Just Another Girl" (2013). He established his own agency, iNKODE, last year.

To find out more about Kim Jae-joong, visit Celeb Confirmed!

BY KIM JI-YE [kim.jiye@joongang.co.kr]