The Lady of the South Tower

That's the name everyone calls the king of Founders's oldest daughter, Elys, who is locked up in the South Tower of Banmaden. The founder king, Geisbach, confined her to the walls of a dusty room in the tower, and she had since thought of that small space as the whole of her world.
Decades after, when one of Elys's younger brothers inherited the throne and she had a chance to escape, she stayed at the Tower, thinking things would never change. However, when her brothers take her to the human realm in search for the girl with a special heart to continue their bloodline, things do start to change..