Taken from drama of the same name
After his mother is brutally murdered in front of him by the Thai criminal syndicate Cheongbang, Lee Soo Hyun is adopted into NIS agent Kang Jung Ho’s family. Together with Kang Min Gi , Jung Ho’s son, Soo Hyun becomes an NIS agent. When Soo Hyun met Suh Ji Woo they were about twelve years old and has another fateful encounter with her 13 years later. Together they had promises for the future.
One day, Soo Hyun leaves for an operation dealing with the Cheongbang, only to return in failure because of the resurfacing terrible childhood memories of when he was in Thailand. The chief of NIS agents, Jeong, proposes to the distraught Soo Hyun to infiltrate the Cheongbang. Through Chief Jeong’s proposition, Soo Hyun becomes an undercover NIS agent after staging his death. Hiding his past, Soo Hyun infiltrates the Cheongbang with revenge in mind, leaving Ji Woo behind. Under the pseudo-name of Kay, he passes through the backstreets of Bangkok. What Soo Hyun didn't know was Ji Woo is the daughter of the same villain, who killed his mother and father.
[source : D-Addicts.com]

Sun-hyuk's grandfather has passed away, and now he's left with tons of money that he should be able to spend. But there's a catch to this will. He inherits the money, but also a housekeeper, a housekeeper-in-training, a lawyer (former bum), a distant relative, and even a girl he doesn't even know!
This girl, Jae-young, is the start of all of his bad luck. First, Sun-hyuk's nametag and his car keys get stolen. Now, he's about to be charged for driving as an unlicensed minor and for bribery. How is he going to get out of this mess? Will his grandfather help him from heaven?
(Source: DramaQueen)

The spam-mail boom of the near future: The great advances of technology, a new generation of improved systems, and ideal computer programs have caused a backlash. The IT world has advanced significantly to the point where humanoid "Spam" mails are causing trouble for their humans. In the near future, hundreds of thousands of spammers have caused incalculable destruction to the mainframe of the lives of everyday citizens. Enter "SM" Hunters to save the humans from our own creations. Can "Spam" ever be good?