Madan no Ou to Vanadis

In a fantasy version of Europe, a war between enemy countries is brewing. One of these countries, Zhcted, has its seven regions ruled by War Maidens, known as Vanadis. Equipped with powerful dragon-carved weapons, Eleonora "Elen" Viltaria, one of the Vanadis, launches an invasion against their neighboring rival country of Brune. Eventually, Tigrevurmud "Tigre" Vorn, a young archer and an earl for Brune's region of Alsace, has his entire army decimated at Elen's hands. In a strange twist of events, Elen spares Tigre, and gives him the order, "Become mine!" What could be the meaning behind this new alliance?