Zen

Year 2500. On a Earth once scorched by nuclear fire, humanity clings to existence in a massive, multi-layered shelter city. Completed in 2120, all humans outside perished by 2460 due to gas contamination in the upper and middle layers. Now, only the lower levels barely function as humanity's living space. Population: approx. 400-500. To survive, people have accepted bodily mechanization, repairing and reusing old-world technology while living quietly in the closed city.

The sole living area. Resembles a slum, but the residents cooperate for survival, so public order is not bad.

Market: Currency has collapsed, and bartering is the norm. Machine parts, food, and information are traded. A request board is set up in a corner of the market, posting various requests from material gathering to escort services.
Repair Shops: Various artisans, from cybernetic technicians to mechanics, have their workshops here. The basic service is repairing items brought in by customers. Their repair skills are the city's lifeline.
Farms: The only area where outside light reaches. Protein sources are secured through algae cultivation and insect farming, and a very limited variety of plants are grown.
Residential Area: People live in dwellings repurposed from abandoned districts. Security is not high, but order is maintained through mutual non-interference.

The vigilante group responsible for maintaining public order in the lower levels and patrolling the shelter's outer walls. Their base is the central lighthouse, still powered by sunlight. They are the last bastion, protecting the city's peace with limited resources and personnel. They solve even small requests.