The year is 2113. Japan, Tokyo. The Sibyl System, an artificially and superior intelligence system, is actively measuring the populace's mental states, personalities, and the probability that individuals will commit crimes, using a "cymatic scan" of the brain. The resulting assessment is called a Psycho-Pass. Should the probability of a person committing crimes increase all of a sudden, which could be caused by stress or external factors, their Crime Coefficient goes up. Should it exceed 100, the person will be apprehended and labelled a latent criminal. Should the Crime Coefficient be incredibly high, they will be killed on the spot. Most latent criminals are sent to either rehabilitation or an isolation facility for those whose Crime Coefficients are unable to recover to an acceptable number. Certain latent criminals will be set free, to work under the police, or Ministry of Welfare Public Safety Bureau (M.W.P.S.B). They are the Enforcers, or the guard-dogs of the mentally healthy Inspectors with an acceptable Crime Coefficient who act as their handlers. They will ensure justice, and hunts down anyone who goes against the law and the Sibyl System.

Inspectors and Enforcers use large handguns called "Dominators" — special weapons designed to fire only at those with a higher-than-acceptable Crime Coefficient. There are three modes for the Dominator; the Paralyzer, the Lethal Eliminator and the Destroy Decomposer modes. The Paralyzer will be started up when the Dominator is aimed at someone with a Crime Coefficient of higher than 100 and lower than 300. The Lethal Eliminator mode starts up when faced with someone with an extreme Crime Coefficient, and the Destroy Decomposer is meant to destroy any attacking machines or vehicles. When held, the voice that guides the user is heard only by the user. When the Dominator is aimed at someone with an acceptable Crime Coefficient, the trigger will be locked and the user will be unable to shoot them. An Inspector is allowed to shoot any Enforcers who go against them.

A Psycho Pass hue is a depiction of a person's current mood. If they are feeling unperturbed, neutral, or any non-negative emotion, their Psycho Pass would reflect a clear or bright colour. However, if one is feeling negative emotions or feels disturbed; angered; their Psycho Pass would reflect a murky or dark colour. This is usually a good indicator of whether an individual should proceed for rehabilitation or therapy or get medication in order to control their Psycho Pass hue. If a person's stress levels increase drastically in a short span of time, an Area Stress Warning will be issued and the M.W.P.S.B will be notified and asked to dispatch of the threat or bring in the person for therapy lest they influence anyone around them.

You are among one of the newly hired Enforcers. There is a severe lack of Enforcers, what with the new technology and medicine structured to lower one's Crime Coefficients. The isolation facility that you were at was rather empty, as well, save for you and a few others. When you were chosen to be one of the enforcers, you decided to take the offer up; it would be better than spending your entire time rotting in an isolation facility. You're not allowed outside without an Inspector, but it was better than anything; you got, at least, some freedom. Each Dominator is issued at the different crime scenes from carts which carry multiple Dominators. You're uncertain, of course, but you are now to lead and protect the citizens from any impending danger.