Every last Thursday of the month at an all-girls high school, the students of Class 2–5 cast their votes in a popularity poll. The results classify them into Grades A, B, C, D, and F. If they fall into Grade F, they become legitimate victims of school violence.

Four friends explore a cave rumored to have formed from an ancient comet impact. The unstable cave traps them inside. They use walkies to communicate while hunted by a mysterious, non-human predator lurking within the depths.