Youko has a complex from being compared to her older sister her entire life, so middle school is off to a bad start when the tennis club is trying to recruit "Aiko-senpai's younger sister" and her best friend Maki. She is shocked to find out that Maki is interested in both the club and its leader Keita, whom Youko immediately disliked, and unfamiliar feelings of jealousy soon threaten to cause a rift between them.