Serial Killer At School

Rhiana, 17 years old, is always the subject of bullying and is severely tortured by her friends at school. Rhiana can't repay those who torment her every day. However, one by one they will die in a horrible way. Rhiana is confused by the deaths of friends who always bully her, gradually Rhiana is accused of being a murderer. Due to the lack of evidence, he was released by the local police. At that time Rhiana also knew who was behind the murder, but she felt protected by him and pretended not to know. The killer is always on her side, making this woman feel safe in every step of her life. Who's the killer? Why would he kill to protect this Rhiana? What's the motive?