Through their tutor Fuutarou Uesugi's diligent guidance, the Nakano quintuplets' academic performance shows signs of improvement, even if their path to graduation is still rocky. However, as they continue to cause various situations that delay any actual tutoring, Fuutarou becomes increasingly involved with their personal lives, further complicating their relationship with each other. On another note, Fuutarou slowly begins to realize the existence of a possible connection between him and the past he believes to have shared with one of the five girls. With everyone's feelings beginning to develop and overlap, will they be able to keep their bond strictly to that of a teacher and his students—or will it mature into something else entirely?

Fuutarou Uesugi's efforts as the Nakano quintuplets' private tutor are finally paying off. The academic performances of the five sisters are steadily improving, and they are each closer than ever to achieving their respective dreams. However, it appears that Fuutarou has become more than a teacher for the girls, who urge him to sort out his feelings. The undecided young man promises to make a decision by the end of the school festival. However, Fuutarou's task will not be easy, as the Nakano sisters pull out all the stops to win his heart before it is too late.

Miyu Suzuki is a high school girl whose cheerful outlook on life is tempered by her need to fit in. Coincidentally, beside her in the classroom sits Yuusuke Tani, a boy unconcerned with others' expectations. Their exchanges rarely extend beyond brief discourse, yet the polarity of their demeanors unexpectedly draws them to one another. As their mutual interest grows, the newfound feelings are no longer easy to ignore. Eventually, Suzuki voices what is inside her heart, forcing both of them to confront the unspoken affection between them. With each passing moment, their relationship evolves, and they gradually come to better understand themselves and the person who is their polar opposite.

Back in middle school, Arisu Yamabuki's only solace in life was a radio show hosted by a girl named Apollo. He used to faithfully tune into the program every night until she abruptly stopped broadcasting entirely. Despite having very few clues about Apollo's identity, Yamabuki has thoroughly investigated her, which eventually led him to enroll in the newly co-ed Furin High School, hoping to find her there. Just as Yamabuki suspected, the broadcasting club's first announcement is made by the familiar voice he admires! Upon entering the club room, however, Yamabuki realizes that his search will not be that easy. The four members—Rikka Inohana, Shinobu Uzuki, Nene Himekawa, and Iko Kirino—all sound like Apollo in different ways. Yamabuki joins the club primarily to find Apollo, but he soon discovers that each girl aspires to pursue her own career with her voice. Seeing that there is a lot of room for improvement, Yamabuki takes it upon himself to help the girls reach their individual goals—but he never stops looking for his favorite Apollo.