Villain's Harem Returns - Chapter 12: The Malevolent Blood

The end of the world is coming, the world has undergone great changes, and everything has changed. Plants, animals, and even insects, as long as there are living things, have mutated.
Become more powerful, and even evolved supernatural abilities, such as chickens and ducks that can fly to the sky, such as cats and dogs that can breathe fire.
But only humans, without any obvious changes, seem to have fallen from the top of the food chain to the bottom of the food chain overnight.
Any creature that can open its mouth to eat can treat humans as food.
But fortunately, this world has not completely killed humans. Gradually, humans discovered that they had the ability to cultivate compatibility with other creatures.
As long as it has a high degree of compatibility with some powerful mutant creatures, it can be used for its own use to achieve the purpose of protecting itself.
Fang He is a person who is very compatible with mutant animals, but it is also because of his ability that he has changed from the strongest to the stupidest.
Fang He, who was reborn, said, “Hmph, this time…”

- Description from novelbuddy

Julian, the son of Duke Alden and the grandson of Grand Duke Augustus stood Infront of the crystalline ball that emanated mana.The crystal absorbed his mana and started glowing with purplish hue, with a sparks of lightning.“Yes, I have unlocked Lightning Affinity,” Julian said, a spark of excitement lighting up his blue eyes.Suddenly, the ball began absorbing too much mana, Julian's eyes widened in horror as the energy swirled out of control, crackling with an intensity that was and terrifying. Just as he realized the danger, the ball erupted in a blinding flash, a shockwave of power surging outward.Julian wasn't hurt, but he felt a strange sensation as a dark mist swirled in front of him. Suddenly, he saw a strange entity, a shadowy figure, slip into his forehead.Then, Julian heard an unfamiliar sound echo in his head:“WELCOME TO THE MILF SYSTEM.”Connecting....SuccessInitializing.......Success“FUCK THE MILFS AND GET STRONGER, CONQUER THE MILFS, CONQUER THE WORLD.” , The voice saidCuriosity piqued, Julian quickly asked, “Can you tell me more about the MILF SYSTEM?”The voice continued, ”Sure, The MILF SYSTEM will help you reach unimaginable power as a mage. You will need to complete the tasks assigned to you and earn points.“

Bai Xunyin was inadvertently traumatized by stress during the year she graduated from Middle School. She became a “little mute” who couldn’t speak. In her first year of high school, she spent her days listening to the cynicism and discriminatory bullying of people around her until her second year of high school. Bai Xunyin met Yu Luoyin. He was clear, elegant, with straight eyebrows and star like eyes. He was the most handsome boy in school, and was the dream boyfriend of all girls in school. But for Bai Xunyin, Yu Luoyin was the first to protect her, smile at her, discuss topics with her, and the person who had lunch with her. The onset of her crush was turbulent and confusing in her teenage years.

Our protagonist Caam is a man from Earth that was reincarnated into this world as a demon. In order to survive, he spared no effort in avoiding the sparks of battle and without noticing it, he became strong himself.