Song Ji Hyo- Main Lead

Park Chanyeol- Main Lead

Song Mino- Ji Hyo's younger brother

Kim Myungsoo-Ji Hyo's partner

EXO- Chanyeol's friend

Song Ji Hyo is a secret agent for the GIA(Global Intelligence Agency). GIA is a foreign intelligence service of worldwide based in U.S, tasked with gathering, processing and analyzing global security information from around the world,primarily through the use of human intelligence. Ji Hyo is one of the best agent in GIA. She has the best record in covert action with 98% success. She was the best student in National Intelligence University. She is also known with her remarkable and amazing martial arts skills. She also has the highest IQ in GIA;180.

Song Ji Hyo was a successful agent until one day, she had to kill a person,who she treasure so much.Because of that incident, she shut herself from the world. She run away from GIA because she knew that they will erase her memory if she want to quit being agent . Ji Hyo then moved in to the city of Seoul, South Korea.  There, she met her neighbour, a bunch of really loud boys living together . Despite being her emotionless and expressionless self, she experienced something that she never had experienced before. Also, big dark secrets start to reveal after that one night ..