"Vendemiaire no Tsubasa" is set in a world where humanity is under constant threat from mysterious, otherworldly creatures known as "Astrals." These beings emerge from portals called "Gates," wreaking havoc and endangering human civilization. To combat this threat, a specialized military force known as the "Winged Guard" is established, composed of individuals who wield unique weapons called "Wings," which are powered by the energy of the Astrals themselves. The story primarily revolves around a young soldier named Aoi, who joins the Winged Guard after a personal tragedy involving the Astrals. Aoi's journey is marked by his struggle to master his Wing, a rare and powerful weapon that carries a dangerous burden. As he trains and fights alongside his comrades, including the determined and skilled commander Shizuku and the enigmatic veteran soldier Kaito, Aoi uncovers deeper secrets about the Astrals, the origins of the Gates, and the true purpose of the Winged Guard. The narrative explores themes of sacrifice, camaraderie, and the moral complexities of war, as Aoi and his allies confront not only the external threat of the Astrals but also internal conflicts within their own ranks. The story builds toward a climactic confrontation that challenges the characters' beliefs and forces them to make difficult choices about the future of humanity.