- In 2043, drastic global climate changes triggered a "red tide disaster": methane permafrost erupted on the Pacific Ocean floor, red poisonous fog swept across the world, light decreased sharply, temperatures soared above 50°C, and 70% of the earth's surface was covered by high-temperature red tides.
- Toxic mist is highly corrosive, and long-term exposure can cause skin ulcers, organ failure, and the birth of mutated organisms (such as the high-temperature-resistant "Red Mist Lizard" and "Corrosion Worm").
- Human survivors gather in a small number of "fortress cities", using high-tech protective shields to resist the red tide and mutated creatures. The cities are connected through underground maglev channels, and resources are extremely scarce.
