Maiden Rose Series by Fusanosuke Inariya

Two soldiers from warring countries are bound by a pledge as master and servant. Taki Reizen is a Commander of sublime beauty, shouldering the fate of his nation. Called "Mad Dog" because of his rough temperament, Klaus has sworn his loyalty to him as a knight. Despite this, those around them are cold and disapproving, full of various misgivings. For all their genuine feelings, what will come of love made cruel by the violence of war?

Klaus von Wolfstadt, from one of the nations of the "Western Alliance," has left his duty as a soldier to his nation in order to be a knight to Taki Reizen, commander of the 15th division "Maiden Rose," whose country has an alliance with "Eurote," an enemy of the Western Alliance. The story follows their romance as it evolves from friendship, to love, and finally, to hatred!