Ever since she was young, Youko has developed a sense of inferiority due to constant comparisons with her older sister. Thus, when the tennis club targets both her and her best friend Maki with offers to join as "Aiko-senpai's younger sister," Youko's start to middle school is anything but pleasant. She is caught off guard when Maki shows interest in both the club and its leader, Keita, whom Youko immediately dislikes. As a result, Youko experiences a newfound emotion of jealousy that strains her friendship with Maki.
