The Strongest Dandy in the City - Chapter 8 Accidental Encounter

This world is sick; both Immortals and mortals suffer from a stubborn ailment known as Longevity.Under the influence of Immortality, various Cultivation Techniques evolve rapidly in grotesque and inexplicable directions.[Fetal Period: A baby is born with shriveled, powerless limbs.][Childhood: After 20 years, the Internal Organs completely decay.][Weak Crown Period: At 50 years, the flesh dries and withers.][Thirty Years Old Stage: After 100 years, the blood runs dry and gives birth to mutations.]I am an Immortal Seeker, and also one seeking survival.

Jiang Bai woke up one day and found with shock that he had transmigrated to a parallel world that is similar to Earth. There, he was granted a cheat system to help him forge the path of a tyrant in this new world. He was now stuck in this parallel world body, the body of a weak and cowardly person. Join Jiang Bai as he rose to the top in this new world!

- Description from Novelupdates

There was no warning and it took them by surprise when the meteorite hit the earth. They thought they were doomed, but they managed to survive the apocalypse. They lost billions of lives because of that incident, and it took them decades to be able to stand on their own feet, but when they thought that they were fine, they were wrong. They found out that the meteorite brought something with it, they discovered a species and they called them Extrateressterial Parasite. It devoured and consumed anything that was alive, and they realized that the apocalypse was just the beginning of their suffering.

After centuries of trying to survive, Archie Lancaster the one who believed the end of humankind could be changed decided to do his best and tried to become one of those people that prevented humankind from extinction. His path wasn't easy nor peaceful, nothing could be described what kind of experiences he had been through.

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.