Only the heart is what is desired for one to strive to survive, but only in means to kill a royal will the truest heir be born. Nerina Sandra Sparrows, a Sirenkiller and a Princess pursues to hunt down sirens who murder by devouring on human heart. Sierra Nicholas Clover, one of the twenty two princesses that has the desire to rule over the sea and her mother the Sea Queen who cherishes the traditions of being presented with a royal heart to resign from her position. Will the two become what they hate? Or will they embrace what they despise?