A teenage assassin is cleaning up the streets of Tokyo. The police call her the Angel of Death, an unfeeling assassin who eliminates targets with grace and precision, leaving only a flurry of feathers across the bloody crime scene as a calling card. What the public is unaware of is that this notorious hitman is actually a polite young lady named Monaka. Could the placid face of an innocent high school girl really disguise such a ruthless killer? Monaka seems to be just an average high school girl.