Kivotos is a federal megalopolis comprising thousands of schools and is led by the General Student Council (GSC), which acts as its governing body. Ironically, despite being an academy city, Kivotos is rife with gun violence, and all students wield firearms as part of their everyday lives. As if the crisis in Kivotos was not enough, the GSC president is nowhere to be found. Fortunately, before her sudden disappearance, the GSC president enlisted the help of Sensei—a teacher who is most likely the only one in Kivotos—to support students in their time of need. Sensei's first course of action is to assist Abydos High School, a once prestigious academy now with merely five students in attendance. These remaining students are doing everything they can to pay their academy's crippling debt of almost one billion yen.

Freshly graduating middle school, energetic 15-year-old Hiyori Suzumi moves from her coastal hometown to Tokyo, pursuing her dream of being a track and field runner. Unfortunately, as soon as her first high school year begins, she faces an imminent problem that ultimately causes her to find a part-time job to cover living costs. After searching through countless prospective workplaces, Hiyori stumbles upon a posting looking for event staff, to which she gets accepted against all odds. It is revealed that she will be working as a manager-in-training for LIPxLIP, a rising male idol group composed of Yuujirou Someya and Aizou Shibasaki—both of whom are coincidentally her classmates. Despite this shocking revelation, Hiyori is resolved to do her best with balancing her studies, her ambition, and most importantly, her role as LIPxLIP's attendant.

Miou Aida and Haruki Serizawa might seem like polar opposites to those around them, but as the two third-years prepare to end their high school experience, they couldn't have been closer. While Miou is a shy and reserved member of the school art club that prefers to stay out of the limelight, Haruki is the boisterous and confident ace of the movie club, already winning awards for his directing prowess. However, after a previous chance encounter during their school entrance ceremony, they quickly become friends despite their stark differences in personality. But although their closeness might be growing, they've never become anything more than just that, much to the bewilderment of their friends. As their time in high school draws to a close, Miou and Haruki, along with their friends in the art and movie clubs, have just one year left to face their hidden feelings and the daunting task of deciding their future careers. The two might always be only an arm's reach away, but as Haruki chases his dream of becoming a professional movie director and Miou struggles with choosing a path for herself, they'll learn just how hard it is to get past those last 10 centimeters.

As another school year begins drawing to a close, the third-year high school students move steadily toward the next milestone of their lives: graduation. Among them are Mio Natsume, a girl burdened with lingering feelings; Hazuki Morikawa, a member of the concert band but distant from the others; and Haruto Souma, an athlete obsessed with baseball. Meanwhile, second-year student Ena Komiya seeks to revive the photography club to its former glory, refusing to let the organization be disbanded. Though this group lacks a strong connection with one another, their lives suddenly cross paths with the arrival of a third-year transfer student. While a transfer so close to graduation is unusual for most, it is business as usual for Eita Izumi. Due to his father's work, he has never been able to stay in one place for very long. But as luck would have it, their most recent relocation has returned Eita to his hometown for his final semester of high school. For better or worse, it also sparks the rekindling of old relationships left behind in the past. With graduation already causing its own share of anxieties, Eita's sudden arrival brings these students' carefree days to an abrupt end. Long-forgotten memories, deeply buried emotions, and inspiring new passions—everything is brought to light in their bittersweet final semester.