My name is Atoris, and I transmigrated to fifth-century Britain.
But I'm not worried at all, because I'm a prince of the Saxons, and my mother is the White Dragon Queen.
Knowing history, I decide to persuade my mother to unite Britain as soon as possible. When Rome is eventually overrun and the continent falls into chaos, we'll seize a territory there. Then we can advance or retreat as we please, and restoring the glory of the Roman Empire will be just around the corner.
That is, until I hear that there's someone in Camelot named Artoria...