Gatenshi

A biological weapon called the "Gatenshi", or "Starving Angel", is running rampant throughout the world because of a mysterious terrorist organization. Its devilish hands extend even to the secluded St. Olivia Academy, where the school building quickly becomes a sea of blood... In an attempt to survive, the remaining students obtain the "D Engine", but that is where their true hell begins...! Source: Shogakukan