Date Masamune's Hatajirushi.(Black flag, and Black feather on top )
Hata-jirushi (旗印?) were the most common of war banners used on the medieval Japanese battlefield. The term could be translated to literally mean symbol flag, marker banner, or the like. Unlike the later nobori, which were stiffened, these banners were simple streamers attached to a shaft by a horizontal cross-piece.
Hata-jirushi served much the same purpose as the nobori, which replaced them, identifying and distinguishing regiments or sections of an army.