Finally, the night of her sixteenth birthday arrives. She expects it to be a wonderful day spent with her peace-loving father, Il, her servant and friend Hak, and her cousin Soo-won, who she had feelings for... However... That night, Yona goes to visit her father to tell him how she really feels, because he opposes to her getting married to Soo-won. However, when she gets to her room, she encounters a shocking truth. The destinies of Yona and the Four Dragons entwine in this period drama fantasy romance!