The story centers around a graduating class of "less-gifted" students in a private Versailles high school. Only a miracle has brought the students this far along, and after a practical joke misfires and the whole school is dynamited, the students are in deep trouble. They have to present themselves in court for their punishment and it could not be worse: If they don't pass their high-school graduation exams, they go to prison!
The students of class 3-E have a mission: kill their teacher before graduation. He has already destroyed the moon, and has promised to destroy the Earth if he can not be killed within a year. But how can this class of misfits kill a tentacled monster, capable of reaching Mach 20 speed, who may be the best teacher any of them have ever had?