Once upon a time, the kingdom of Kouka was ruled by a red dragon in human form. By his side, four warriors imbued with dragon blood helped him lead the kingdom to prosperity. Time passed, and this tale became a legend to tell children.

As the sole princess of Kouka, Yona lives a life of lavish ease. In love with her cousin, Su-won, and protected by her bodyguard, Son Hak, she wants for nothing and remains sheltered from the harrowing reality outside the castle walls. Contrary to this peaceful illusion, Kouka is about to undergo a political upheaval. After her beloved Su-won stages a bloody coup and murders her father, Yona is forced to flee with only Hak by her side.

Though surrounded by enemies on all sides, the banished princess still yearns to save her kingdom. Her solution comes from an exiled priest, who tells her that her only hope is to find the four legendary dragon warriors. Guided by this seemingly fictitious myth, Yona sets out to find these warriors, determined to restore her kingdom.