Tokoshie x Bullet: Kaijuu Gakuen

A decade after a massive biological weapon, operated by a terrorist organization known as the Tokoshie, devastated humanity, Tsukimi leads a solitary life at high school. A distracted new student arrives and randomly selects Tsukimi as his "partner," leading to a sudden shift in Tsukimi's routine. What was once an uneventful academic experience transforms into a situation with implications for the entire human race.