Seo Joo-Hyun isn't the innocent girl you've known. She's actually an ellite spy/agent working for South Korea with her brother's Choi Jung Su (Leeteuk) and Choi Siwon.

And her real name isn't Seohyun, its Choi Yuna. Yuna and her brothers are trained ever since they were little kids. South Korea has been recieving terrorist everywhere. The NTS (National Anti-Terror Service) has been sending their best agents to help.

Siwon, Jung Su, and Yuna have been busy with their schedules as the two top K-Pop groups, Super Junior and Girl's Generatoin (SNSD), but they still have to complete their duties as a spy.