Claudia de Porto is a dear princess of Porto who was about to have the most perfect 19th birthday party with her brother Juverin, who had prepared her birthday party to be everything she dreamed of, and Prince Kim, who was going to propose to her. However, right in the middle of Prince Kim's proposal, Porto Castle bursts into flames from Demon King's attack. Later, Claudia finds out that her kingdom has lost its valuable treasure and her brother a heart from the attack.

Claudia falls into the great spirit Desire's plan and becomes the next hero to save her brother and her kingdom. But... she has to go on the journey with her ex-fiancé, Demian Alphen. Will Claudia, who grew up sheltered by her brother Juverin her whole life, be able to cross the forbidden sea of death and get everything back from the Demon King?

This is a story of a clueless princess becoming the next hero of the world through a journey she goes on to save her brother and her kingdom.