On the first day of senior year, Lin Xia discovers blood seeping through the classroom walls. With the whole class trapped in an endless loop of dusk, an electronic voice announces the first rule: [Do not touch the skull wind chime on the classroom's back door]. To find clues about her missing mother, Lin Xia is forced to form an "Alliance of Survivors" with classmates of all kinds. Together, they uncover the dark secrets buried in the education system as they navigate a warped high school instance.
When the slogan "Exams are a battlefield" becomes a living hell, and school rules turn into killing decrees, they discover that every instance corresponds to a real-life case of a high school student's death. And inside the chalk box left behind by Lin Xia's mother lies the ultimate weapon for destroying this experiment in human nature: an exam paper covered in answers written in blood. It turns out to be the code to clear the game, bought with the lives of the previous generation of resistance fighters.
