Yonna in the Solitary Fortress.

From a young age, Yonna and Stan have been outcasts from society due to Yonna's magical abilities. Hence they stay in a castle away from others who seek to persecute them. The Imperial government over time, recognise the potential of Yonna's powers to benefit society, but Stan rebuffs their approaches. Now years later, Garuda, a young Imperial agent is sent to retrieve Yonna from the castle. To complicate things Piggott, another Imperial lackey, has lied his way into the castle to fulfill his own objectives. [From AnimeNewsNetwork]