The drama has now revealed a set of character posters leading up to the drama's premiere. EXO's D.O. looks solemn and serious as his original role of the crown prince Lee Yool, standing in front of numerous coral umbrellas. On the contrary, Nam Ji Hyun looks serene and peaceful with a lovely smile, and her character poster unveils new information about her character Hong Shim - she has been hiding her true identity, the daughter of a wealthy, upperclass family named Yoon Yi Seo!

It turns out, the crown prince isn't the only one with two different 'egos' in the series... to catch more of the story unfold, stay tuned for '100 Days My Prince' beginning on September 10!