On the first day of school, five new students are asked by a forgetful teacher to find a password for his laptop.

Pizza that was left in the teacher's office disappears and the suspicion points at the five members. To prove their innocence, they go around and investigate others that were in the teacher's office.

The girls manage to find clues and obtain the number code to successfully open the Mystery Club's door. When they get inside, they witness students bullying a classmate.

The girls take the S-Class entrance exam. Later, they return to their hideout and try to complete a mission by solving cases in the case box.

The five members find out that all the secrets of this school have something to do with the elite class and hear that someone has cheated on the last entrance exam.

The five members go through the footage from the surveillance camera to solve the mystery of the English exam. Later, the members find another clue in the library.