In Sabage-bu!, Momoka Sonokawa begins her new middle school life with a nightmare commute: on the train to school, she is targeted by a molester and rescued by a girl wielding dual pistols. That girl is Miou Ootori, Momoka's upperclassman and the president of Aogiri Academy's Survival Game Club, known as Sabage-bu for short. After noticing Momoka's aptitude with a pistol, Miou decides she wants her in the club and keeps pressing her to join. Even though Momoka refuses at first, she somehow ends up becoming part of Sabage-bu anyway.
What Momoka finds inside the club is far from normal. Sabage-bu is anything but a typical middle-school club, and its members' socially awkward behavior unnerves her from the start. Their personalities range from fanatical to completely delusional, and their antics push school life into absurd territory. They do not hesitate to roam public areas in ghillie suits or even go bungee jumping from the school building. Thrown together with this collection of survival game maniacs, the outwardly ordinary Momoka has to adapt to a school life that is chaotic, bizarre, and much wilder than she ever expected.