Ga-Rei: Zero

An elite squadron trained to combat supernatural forces is called in to investigate reports of invisible monsters terrorizing Tokyo, but their mission is complicated by the interference of a rogue exorcist. When the mysterious female slaughters the overmatched attack force, her former comrades are ordered to lock down the crime scene—and forever silence their old friend. (Source: Crunchyroll) Note: This series is a prequel to the manga series, Ga-Rei.