When Yuna Lee's mother moves to Germany to pursue a music degree, she's left to stay with her father, a university professor, and her three older brothers, who are fiercely overprotective of her.

During her summer vacation, she visits her mother in Germany, where she falls off a cliff and is rescued by Rieno, an 18-year-old knight living in the land of Phantasma. Rieno makes a deal with Yuna: If he saves her life, she must come with him and become the Queen of Phantasma.

After agreeing, she goes back home, only to return to Germany some months later, and is whisked away to Phantasma by Rieno. Now, she must cope with being the Queen of Phantasma, while forgetting the world she came from.