Kim Seokjin is a Prince in the royal family and Moon Byulyi is the long-suffering Captain in charge of his protection. The heir to the throne - Kim Yongsun - is soon to be married and her fiance's family is arriving on the eve of the Royal Games. The games are always dangerous but this year there is an assassin in their midst. With the Royal children participating in the games, Byulyi must join to protect them and flush out the assassin before it's too late. However, not all is as it seems and Byulyi's job would be a lot easier if a certain Prince didn't keep trying to distract her by befriending her. But it's all in a day's work for a Captain of the Royal Guard.