From Baka-Tsuki:
In times of war, set in Western Europe, Eleonora Victoria, one of the seven Vanadis of Zhcted, leads the war into Brune. There are actually seven Vanadis, named like this because they each received a powerful weapon from the dragon, to reign over seven territories, each possessing their own. The power of the Vanadis causes dread and fear toward their enemies.
An Earl in the service of the country of Brune, a young archer called Tigre, got a taste of it after he was defeated on the battlefield by Ellen (Eleonora). However, Ellen decided to spare his life after seeing his skills. In exchange, he is asked to serve her.