Yuuji Sakamoto is the class representative of class F. In the series, the class rep position is assigned to the smartest student of that class. He is cool, collected, and exhibit surprisingly high intelligence and foresight unexpected of a student from class F. In volume 1, his strategies and tactics had helped class F to attain victory after victory, until the duels with class A in which he overestimated his ability in elementary school level Japanese history. Yuuji was once known as a child prodigy in his childhood. The only reason why he ended up in class F was because he did not study at all and he holds the strong belief that grades are not everything. However, due to the consequences he 'suffered' from his defeat from Shōko Kirishima, his childhood friend and also the top student of his level, he became motivated to study again, and in the later volumes, his Shoukanjuu became reasonably strong in just a few months due to his test scores improving by leaps and bounds.

It is implied that he is actually smarter than his childhood friend, Shouko. After the tournament in volume 2, he acquired a platinum bracelet which allows him to control the size of the force field of his Shoukanjuu, allowing him to form a one-man army choke point since humans cannot pass through this force field.

He bears no ill intention towards Shouko, but due to her unyielding obsession with marrying him since their childhood days, he sees her as having a few loose screws in her mind, and fears to even think of his future if he does marry her. In the anime, its suggested that they act like a married couple though she tends to treat him as a slave. Yuuji is close to Akihisa to the point where they can actually communicate without any words. A gag in the series is that Yuuji will attempt to decipher a complicated expression on Akihisa and comment on a series of events that must have taken place. While he meant it as a joke, he is always a spot-on when this happens. His Shoukanjuu wears an outfit that makes it look like a punk, and is armed with brass knuckles.

(Source: Wikipedia)