Five years ago, a plague wiped out a great part of the land of Fortna's population. Nina, a girl with unique, deep-blue eyes, counts her parents among the casualties of the pandemic. In order to survive, she teams up with a pair of fellow orphans and begins to steal from the wealthy. Unfortunately, Nina's life is struck by tragedy again as she finds herself being abducted by a group of mysterious men.

Her main captor turns out to be none other than Azure Seth Fortna, the second-born prince of the royal family. His half-sister Alisha—a reclusive priestess-princess—perished in an accident before she was to be married off to the crown prince of the neighboring kingdom of Galgada. Although Nina does not resemble the late princess in the slightest, they do share one characteristic: their one-of-a-kind eye color. With the intention of preventing a war between the two kingdoms, Azure plans to use Nina under the false pretense that she is the real Alisha.

With nothing else to lose, Nina reluctantly accepts the prince's proposition to replace his late sister. Pretending to be royalty is not an easy feat, but Azure aids Nina until her departure. The fate of two nations rests on Nina's shoulders—and she will make sure the stars are on her side.