This Beggar is a Dragon God

Karen, rightful heir of the Red Dragons, escaped the coup of his stepmother Fiona and half-brother Marcus, hiding as a beggar to temper his Black Dragon Soul. Years later, Isola, the Blue Dragon princess he once saved, kneels before him and proposes in public. Their engagement is cursed, exposing his royal bloodline and Dragon God power; when Fiona and Marcus transform into evil dragons, Isola's Ice Dragon power helps Karen awaken the Golden Dragon God and slay them with his own hands. The two kingdoms forge peace, and Karen weds Isola, ushering in an era of everlasting peace.