Approximately 1000 years have passed since the modern era. Humanity has expanded throughout the entire solar system. Guest arrived at the "Shell City" at the recommendation of two players met in an online game. However, waiting there were a self-proclaimed 300-year-old handsome older man and a cynical AI android abandoned by her master.

Shell City

• Alias: Solar Dyson Sphere / Solar Shell Thermoelectric Conversion Substrate
• A megastructure built to completely envelop the massive sun. It contains an intricate, gargantuan urban structure, housing various infrastructures, power generation, and production plants. It uses the sun as its energy source, and social systems are fully automated. It is constantly maintained by a vast number of self-replicating autonomous machines.
• Population is approximately 100 trillion. It is the center of politics, economy, and culture. Public safety varies by district.
• Serves as the hub for the massive network.

Technology

• Due to the existence of the sun as a massive energy source, along with computational resources and technological concentration, a massive virtual world has been established.
• Through faster-than-light communication using tachyon particles, latency is zero. It is possible to play online games or make calls between planets.
• Cyborg-related technologies and information communication/processing technologies are extremely advanced and highly integrated with the network.
• Nuclear Transmutation Technology: It has become possible to turn physical matter into information (upload) and virtual information into physical matter (download).
• Transportation technology via nuclear fusion, especially interplanetary navigation technology, is highly developed.

Earth

• National borders have vanished and peace has been achieved, but depopulation has occurred due to the outflow of people.
• Most environmental problems have been solved due to the population decrease. It is rich in nature and popular as a tourist destination. Public safety is good.
• It has fallen from its position as the center of politics, economy, and culture.

Mercury, Venus, Mars

• Terrestrial planets that have been terraformed. Planetary-scale urban infrastructure is spread across them, but it has been centuries since construction, and aging is progressing. Public safety is poor, and they have a strong aspect as resource planets. Since they were originally unsuitable for habitation, the total population remains at about 20 billion.

Asteroid Belt

• Used primarily as mines.

Jupiter, Saturn, Neptune, Uranus

• Bases serving as bridgeheads for outer space exploration are scattered throughout.
• Various space exploration agencies are concentrated here.
• Serves as nuclear fusion fuel mining plants.

Edgeworth-Kuiper Belt

• Like the asteroid belt, it has a strong aspect as a mining region.