After her crushing defeat of 21-0 at the National Junior Badminton Tournament, Nagisa Aragaki's love for her sport begins to distort. Unable to deal with the shame of loss, she starts to terrorize the members of her high school badminton club. Her grueling drills bring some to the verge of tears while others quit the club outright. With the team losing members and new prospects being too terrified to join, the future of the badminton club looks exceptionally grim. That is, until Kentarou Tachibana joins as the new head coach. Not only is he an Olympic-level player, but he also comes bearing a secret weapon: Ayano Hanesaki, the girl who defeated Nagisa six months ago. However, Ayano is not the rival Nagisa remembers, but a girl with conflicted feelings wanting to distance herself from badminton. With her future in sports now on the line, Nagisa must find a way to face her fears of inadequacy, heal her rival's troubled heart, and bring victory to Kitakomachi High School's badminton club.

Naho Takamiya's first day of her sophomore year of high school is off to an uneasy start. After waking up late, she receives a strange letter addressed to her. However, the letter is from herself—10 years in the future! At first, Naho is skeptical of the note; yet, after witnessing several events described to take place, she realizes the letter really is from her 26-year-old self. The note details that Naho's future life is filled with regrets, and she hopes that her younger self can correct the mistakes that were made in the past. The letter also warns her to keep a close eye on the new transfer student, Kakeru Naruse. Naho must be especially careful in making decisions involving him, as Kakeru is not around in the future. With the letter as her guide, Naho now has the power to protect Kakeru before she comes to regret it once more.

Former ace runner of Sendai Josei High School, Kakeru Kurahara is chased away from a convenience store for shoplifting. Shaking off his pursuer, he runs into Haiji Kiyose, another student from his university. Haiji is impressed by Kakeru's agility and persuades him to live in Chikusei-sou, the run-down apartment where Haiji resides along with eight other students. Having lost his entire apartment deposit at a mahjong parlor, Kakeru accepts the offer reluctantly. However, Haiji reveals a secret during Kakeru's welcoming party: the apartment is actually the dormitory of the Kansei University Track Club. He unveils his ultimate goal of participating in the Hakone Ekiden—one of the most prominent university marathon relay races in Japan. Unfortunately, all the residents apart from Haiji and Kakeru are complete running novices. Worse still, none of the inhabitants are even remotely interested in being involved with Haiji's ridiculous plan! With only months before the deadline, will the fourth-year student be able to convince them otherwise and realize his elusive dream of running in the Hakone Ekiden?