MTL - My Darling Sick Beauty - Chapter 41

Zheng Yi transmigrated to the Cultivation World, living an unremarkable life and becoming a Loose Cultivator at the bottom of the Cultivation world.Occasionally, he crossed over to the Doomsday World, where millions of zombies are waiting to be materials for his cultivation.

Doomsday comes, and human beings enter the heavenly world.
Ten years later, Yang Chen, who was betrayed tragically, returned strongly with the Tianyu bug. In this life, he vowed to make the betrayal pay the price. He has a powerful bug bonus, just like an open hang. Frightened to hear…

- Description from novelbuddy

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.

No matter how twisted the world becomes, humans will always remain humans.In the face of their doom edging closer, their greed doubles instead of fading away. Their selfishness is unwavering—they simply want everything, even at the cost of endangering those closest to them.For that is the truth of humanity.So, if everything is linked to iniquities and sins, then unlike them, I won’t shy away from these possibilities—I will embrace them.---Synopsis:Kael, a young man from Earth—a dimension renowned for its technological advancements and brilliant minds—returns on a tour sponsored by his school.But fate has other plans.A Dimensional wave crashes into Earth, mutating the entire world into a grotesque landscape of unexplored horrors.Those who survived the dimensional impact awakened to newfound strengths, while those who didn’t perished—or worse—transformed into monstrosities far more fearsome than any beast.The world has returned to the law of the food chain. The strong will endure and rule, while the weak are devoured.Kael must cling to his sanity and navigate this nightmarish new world with a mission: to protect all he has left.But things take a darker turn when the system he acquired reveals an unexpected and horrifying backlash:{Consume human flesh}{Or perish within the next 24 hours}The clock is ticking, and Kael is left to grapple with an impossible choice that could seal his fate—or his humanity.