On a train heading to her new middle school, Momoka Sonokawa is targeted by a molester, only to be saved by a girl wielding dual pistols. This girl turns out to be Miou Ootori, Momoka's upperclassman and the president of Aogiri Academy's Survival Game Club, known as Sabage-bu for short. Noticing Momoka's aptitude with a pistol, Miou takes a liking to her and attempts to persuade her to join the club. Despite Momoka's steadfast refusal, she inexplicably finds herself a member of Sabage-bu. Sabage-bu is anything but a typical middle-school club. The socially awkward behaviors of its members scare Momoka. Their personalities range from the fanatical to the completely delusional. They do not hold back from walking around public areas wearing ghillie suits or even bungee jumping from the school building. Thrown together with this collection of survival game maniacs, the zealously ordinary Momoka must somehow adjust to her unexpectedly wild school life.