Regretful sins of us

The Princess of Light kingdom saved a boy with unknown background when she fell into an abyss.And when he wakes up , he lost his memories..She takes him to her country after they get out of the abyss. According to the rules of light kingdom , a stranger must be kept in the country if they have come inside. She tells him that she will protect him . Days went by , they became closer and develop feelings for eachother . But how strange.. his memories came back when he felt a woman with white hair . Who is he? And according to the traditions of kingdoms , royalties can only marry royalties and he / she must be from the same kingdom or a friendship kingdom. Will they even end up together??