From JanimeS:

Princess is a very straight forward and sad series. This series is full of romance and politics. The background is an unknown medieval era where there are three countries. Among the three countries, there is an island country called "Ramira". The empire, Ramira, is where most of stories will unfold. There are generations of princesses, and the first 27 volumes set the story for the eventual regaining of Ramira by the greatest Empress of Ramira, Preia, who was beloved by the people and had many loyal men under her.