This might be the answer—
In the former old world, the X-17 Strain studied in the manual was sent to Mengxin City and many other places with launch towers, and was released through these towers, knowing the extreme cold was inevitable.
Then, people began to change, or rather, to evolve, becoming resilient to cold, hunger, and able to adapt to such extreme cold, surviving even without heating protection in this terrifying chill.
And it wasn't just humans that underwent these changes. The hyenas, wild boars, packs of wolves, fish, and shrimp once encountered also passed through winter after winter in this cycle of day and night.
But what exactly happened in the world back then? People had long been aware of the coming winter, was it pure foresight? Or were there some preconditions for this event?
And these Neo-Humans today, according to the manual, were originally kept as a backup, but have now become the so-called Type A, B, and C Neo-Humans, preserved in this world.
