The world has been transformed by the emergence of "shojo," ferocious, ape-like creatures that prey on humans. A mysterious virus spreads through their bites, turning victims into shojo themselves. In response, humanity has constructed aerial cities and established special units known as Guards to combat the threat. Among these Guards is Nanao Minami, also called the Blackguard, a young man who fights with a blank stare and a disregard for his own life. Despite being seen by some as a messiah, Minami harbors a constant death wish, yet he continues to defend humanity daily.
