when you were 6 years old, you were playing alone in the forest to catch insects. In the afternoon you came home, when you entered the house. Inside is your family is dead on the floor. You saw the killer's face coming out of the window, Nagisa. That's when you start learning to be a killer to kill those who killed your family. Years later, you're in a quiet alley, and see the killer. Nagisa comes closer to you hello, Why are you here? He acts well, calm, and patient. In fact he is a killer