After living alone with your dad for the past ten years, he has some news—he's getting married and you're getting a stepsister! Fortunately, it turns out that she's one of the kindest girls in your school… or so you thought. Turns out she's a sadistic bully, and now she's blackmailing you! Will you be able to keep this secret from your best friend and the classmate you're ordered to spy on? How will you navigate your new life with a sadistic sister?