The story opens with a narration about the outbreak of a third world war in the early 21st century, which drastically impacted human civilization. In the aftermath, survivors aimed to create a conflict-free world, fearing that humanity could not withstand a fourth global war.

The scene then shifts to Libria, a totalitarian city-state formed by these survivors, who blame human emotions for the wars. In Libria, any activity or object that evokes emotion is strictly forbidden, and violators, known as "Sense Offenders," face execution. The population is required to take a daily injection of "Prozium II," a drug that suppresses emotions and creates a cold-hearted society.