Wizrain Oukoku Monogatari: Ryuu ga Hanayome

The Kingdom of Wizrain was founded in the distant past by a great hero and the dragon dear to him. Elna, however, is no hero. She is the daughter of a nobleman's mistress, taken into her father's household only to suffer the cruelty of her stepmother and stepsister, or so she believes, until the day it all returns to her: memories of a previous existence as a dragon. Driven by recollections of flying through the heavens beside her hero, she makes for the royal palace. One glance at the young king, Vaide, convinces Elna that he is the very hero she loved, reborn. The trouble is that he has no memory of her whatsoever.