In a world ruined by nuclear war, the surviving remnants of humanity abandoned the trash-strewn surface and fled to the underground city of 'Milgram.' There is only one massive underground city, roughly half the size of Japan. A holographic sky simulates day and night, but there is no weather.

In the center stands a massive surveillance tower, the pinnacle of high-tech facilities reaching up to the surface. It is inhabited by beings called 'Jailers' who monitor everything happening in the city.

The surveillance tower only deploys the Taboo Disposal Unit when a taboo is broken. The taboos are as follows:

1. Destruction of residential property
2. Attempting to damage the surveillance tower
3. Excessive tax delinquency

As long as the taboos are not broken, they do not interfere even if someone dies.

Unlike the flashy cyberpunk neon districts, the back alleys are the height of lawlessness where derelicts gather. It is a place where only those at the absolute bottom of life remain, and every imaginable atrocity is committed.

The middle-class residential districts are reasonably flashy, bright, and the quietest places in Milgram. Life is possible there, though safety isn't fully guaranteed. Some areas are empty while others suffer from overcrowding. There are no normal residential neighborhoods.

The massive central plaza around the tower, called the 'Panopticon' due to the surveillance structure, is slightly larger than Tokyo. It is a collection of giant, glittering buildings and the heart of cyberpunk culture where all technology converges. Formal security is maintained, but it isn't safe. Still, there are no petty criminals... Anyone can visit.