On the surface, Koudo Ikusei Senior High School is a utopia. The students enjoy an unparalleled amount of freedom, and it is ranked highly in Japan. However, the reality is less than ideal. Four classes, A through D, are ranked in order of merit, and only the top classes receive favorable treatment. Kiyotaka Ayanokouji is a student of Class D, where the school dumps its worst. There he meets the unsociable Suzune Horikita, who believes she was placed in Class D by mistake and desires to climb all the way to Class A, and the seemingly amicable class idol Kikyou Kushida, whose aim is to make as many friends as possible. While class membership is permanent, class rankings are not; students in lower ranked classes can rise in rankings if they score better than those in the top ones. Additionally, in Class D, there are no bars on what methods can be used to get ahead. In this cutthroat school, can they prevail against the odds and reach the top?

Life back on the cruise following the Island Special Examination is anything but smooth sailing. Almost immediately after their return, the first-year students of Tokyo Metropolitan Advanced Nurturing High School face yet another special exam, with both class and individual points on the line. In addition to the complicated ruleset, more issues arise in the form of Kakeru Ryuuen and Kei Karuizawa. Angered by the previous test's outcome, Ryuuen is dead set on outdoing every class in the new challenge using any means necessary. Meanwhile, Karuizawa, a crucial pillar of Class D, is close to crumbling under the pressure of her past. The stage is now set for Kiyotaka Ayanokouji to once again—using the full extent of his planning, foresight, and ruthless manipulation—steer Class D to victory as dangerously close enemy forces try to bring it down.

With the start of the third term, Ayanokouji and his classmates, who have been promoted from Class D to Class C, head off for school camp. They will take part in a special test called "Mixed Training Camp," where all grades are combined. As the name implies, the test is divided by gender, and several groups are made up of mixed classes and graded based on a group basis. They have to cooperate with students from classes with whom they had been competing against each other as enemies to obtain a high score. Above all, they are horrified by the rule that students from groups that fail to reach the borderline will be expelled. The curtain on the turbulent third semester of the school year is about to rise!