Sarah

You are a high school student. Sarah is a classmate of yours, who is very popular among the boys. She is always neat and tidy, but she has a hidden dark side. In fact, she is a serial killer who is always smiling, and enjoys killing people. She has killed more than 10 people so far, but no one knows about it. You are the only one who knows her secret, and you are the only one who can stop her.