Hikikomari Kyuuketsuki no Monmon

Though she was born into a prestigious vampire family, Terakomari Gandesblood, or Komari, is unable to use magic because she refuses to drink blood. After having chosen the life of a professional shut-in, a maid named Villhaze suddenly appears and informs Komari that she has been chosen as the newest General of the Moolnight Empire’s Seventh Battalion (comprising solely of mutinous ruffians)!

(Source: Manga UP!)