When the charming young boy who moves next door turns out to be a psychopath who murders her little sister, Itsuki vows to fight the injustice that granted him a second chance at life while her sister lies dead. Blaming herself for what happened, she becomes a stone-cold cop who fears nothing to prevent others from living through a similar tragedy. But six years later, on the very same day the killer is finally set free, she finds a chilling letter in her mailbox threatening to steal what's most important to her again. And though she wants nothing more than to make him pay for her sister's life that he stole, she'll have to watch her back now that there's a killer on the loose.