In the Vashumira no Shihou (The Crown Affair) series:

Vol.1 - Royal Target

Nothing would stop Nicholas Zared from taking his rightful place as King of Vasmira. Not a bloodthirsty assassin?nor American spitfire Erica Allen. Without the fiery beauty's acceptance of their long arranged marriage, Nicholas would be denied the crown. But it wasn't duty alone that bound him to Ericka, not with desire blazing between them and the discovery that she might be the killer's real target...

Ericka tried to resist the handsome prince's skilled seduction, but their close brushes with death only intensified the passion flaring between them. Would her consent to be his queen cost her her heart?and her life...?

Vol.2 - Royal Mission/Royal Ransom

Vol.3 - Royal Crisis/Royal Pursuit