Killing Dao Fruit - Chapter 67 - 65: Out of the Blue

Masterpieces such as 'The Divine Comedy', 'The Theory of Evolution', 'Encyclopaedia Britannica', 'The Theory of Relativity'...Born in the history of human civilization, possess mysterious and magical powers in another world!Original sin, biological evolution, mastery of all arts...By reading the secret tomes, one can gain a variety of powers!The only trouble for the people of the other world is that they find it difficult to understand the texts from Earth.At this time, there comes a librarian from Earth...

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

Felix's life on Earth had become a series of dead-end jobs, ruined relationships, and rotating apartments smaller than most postage stamps. By all accounts, even his own, he was a coward. Too afraid to move forward, to take risks. Yet when given the chance to choose between risking his life or walking away from a deadly encounter, he didn't hesitate.Moments before his untimely demise, Felix was snatched from earth and thrust into a magical world known only as ‘The Continent’. Empowered by the ‘System,' he learns that he can strengthen himself through combat and dedication. To survive he'll have to push himself beyond his limits, or else fall to the monsters all around him.Levels, stats, and magic. Death is the start of a terrible fate, but if he lives…who knows what he will become.

The story is about a boy entering high school, who answers a strange call from a public phone one night. The caller challenges him to a bet: She’ll remove the birthmark which he sees as the cause of so many problems, and he’ll have fifty days to win the heart of a girl he’d considered far beyond his reach. And with this, a very strange summer begins.