The descendants of humans finally arrived on Earth from the cosmic starry sky, but this was a huge deviation from the plan of their previous generation. They did not appear as conquerors; instead, they faced a severe regression in civilization and even struggled to survive.
These humans, pure as white paper, had just appeared on Earth. Before they could explore this unfamiliar world, half of them were drowned by a global tsunami caused by a space fortress crashing into the Atlantic Ocean. Another half died of starvation later; then another half were eaten by predatory beasts; and finally, another half were killed by various bacteria and viruses...
