Park Jinyu, an assassin born to kill and destroy those who are what she calls 'Trash'. She's in an organisation named Sm and her sub group is named EXO.

Mark Tuan, a member of the group Got7 created by an organisation named 'JYP'. Their job is  to take care of people who are a threat to humans.

Byun Baekhyun an assassin and in the same group as Park Jinyu. He's the closest Jinyu has to family and she cherishes him as her 'brother'.

Two oranisation wants to destroy eachother and what better way to do it then to to send out their best units to do the dirty work?

JYP has gotten out of hand. Jay Park has gone mentally insane and tries to keep Korea 'clean', he kills those who he thinks is guilty(guilty or not once he finds you a threat he will kill you). Soo MAn wants to take JYP down once and for all and Exo holds secret grudges against JYP for killing their loved ones.

Jay Park wants Sm down to avenge his wife's death and revenge for killing his daugher. It's almost like a little game, isn't it? 

 This stroy is based on a killing game and like any other games only one can win. But remember winning isn't that easy. You win some, you lose some and you sacrafice some...