An ordinary college student, Lee Seol, finds out she's a princess. The grandson of Daehan Group, Park Hae Young, is put in charge of educating Seol on proper etiquette.

Kim Hyun Joon is an assassin who belongs to a top secret organization known as the "NSS" whereas T.O.P is an assassin who works in another secret organization located in the United States called "IRIS" and was ordered to kill Hyun Joon. Seung Hee is a psychological analyst who plays an important role in bring Hyun Joon into the "NSS." Jin Sa Woo is Hyun Joon's enemy and falls in love with Seung Hee as well.

Shi Yeon is a Nine-Tailed Fox living undercover in the human world. By day, Shi Yeon is an employee at a natural history museum. By night, she's a top-ranking woman warrior in the Nine-Tailed Fox clan, charged with preserving the delicate balance between man and fox. But her world is sent spinning when an atrocious serial murder - where the victims have had their internal organs gouged out - is uncovered. Detective Min Woo believes the murders may relate to the organ trafficking trade, and goes undercover in a seedy organ smuggling ring. But Min Woo's cover is blown, and it's only through the intervention Nine-Tailed Fox warrior Mu Young and Shi Yeon that he's able to survive! But he's seen their true identities as Nine-Tailed Foxes…can he be allowed to live?