"The Pyramid" is a word referring to the ultimate means of classification, which has been used since ancient times. At the private Saginomiya Academy, where the children of the elite top 1 percent of society assemble, there's one absolute rule: to one-up others and reach the top! Rei Satou, who is the very definition of average, is sure to be firmly planted at the very bottom of the social class and spend three years being tyrannized by the rich and powerful. At this point, the only way for him to survive is to move up to S-class. But to his astonishment, a beautiful, unfamiliar girl named Senri Tsukinami appears before him... and tells him to kiss her?! "Be my boyfriend, so we can work our way up and mount ourselves on the pinnacle of happiness!" Thus, he joins forces with his most annoying girlfriend and aims to reach the top class of the academy!