On a train to her new middle school, Momoka Sonokawa is preyed upon by a molester, only to be rescued by a girl wielding dual pistols. The girl turns out to be Miou Ootori, Momoka's upperclassman and president of the Aogiri Academy's Survival Game Club, called Sabage-bu for short. Noticing Momoka's...

Source: MyAnimeList