My Dear Miss Medical Examiner - Chapter 2

In a world dotted with World Entrances to a demon world, demons have invaded humans for centuries. Humanity has united and one of the most ancient sects in the world, the Archean Mountain Sect, has set up an entire education system in the form of Dao Academies and defenses at the World Entrances.

This world is Heaven.

Because this world has everything you dream of, everything you wish for.

This world is Hell.

Because everyone in this world are parts of a never-ending massacre.

Are you fighting to survive, or fighting to come home?

- Description from Novelupdates

Arthur was a weak and cowardly boy who lacked the power to protect anyone—a truth brutally demonstrated when his parents were massacred while defending him during a Gate outbreak. As the sole survivor, Arthur spent weeks believing his life was over. When intense chest pains began, he assumed he'd been infected with corruption by the void creature that killed his parents and was merely waiting for death.What Arthur didn't expect was that these sensations actually signaled his Realm Core forming. In two months' time, he would be forcefully transported to the next realm and awaken new powers, becoming one of the world-renowned “Chosen” who protect humanity from Gate outbreaks. Now Arthur must rise through the heights of power, climbing each of the seven realms in hopes of saving his world... or does he?

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