The story centers around a boy named Akihisa Yoshii also known as the idiot or the baka of the title. He attends an academy where they rigidly divide the student body based on the result of the tests taken. In this case, the A class is filled with students with high scores therefore, their class were filled with many prestigious items (air conditioners, fancy seats, huge spaces, etc.) while the state of the F class is the complete opposite of the A class, which leaves much to be desired.

On the day of the placement test, a smart girl named Mizuki Himeji had a fever and couldn't complete her test. As a result, she was pigeonholed into the F class together with Akihisa Yoshii. Akihisa, who pitied her, pitched an idea to his class to rule over the higher level classes by doing a summoned being wars for both Mizuki's sake and to get more and more prestigious items. Aside from Mizuki (who happens to be the ace of F class), there's also the class representative Yūji Sakamoto, the bishōnen Kinoshita Hideyoshi, the perverted Tsuchiya Kouta, and the tomboyish Shimada Minami (whom Akihisa claims is his worst enemy).