In a different alternative world, ruled by the social status system with the king at the top. There's a princess, Minatozaki Sana, a beautiful, kind, smart and brilliant girl who has never left the palace.
Despite the fact of having everything she can ask for, there's something she lacks, freedom. Being determined as she is, she tries to escape plenty of times. However, the king gets to keep her under control by making the royal family members have a personal bodyguard.
Although she really doesn't get along with her bodyguard, she somehow feels curious about her brother's one. It's quite normal though, he's the older son of the Hye clan, well known for the military service for the king.
They both know that it's forbidden to talk with each other, but when the curiosity and instant attraction is bigger, then... There's nothing to do.