MTL - Mesmerizing Ghost Doctor - Chapter 9 Jiufulin

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

The handsome Emperor falls in love with a Knightess! Knightess Poliana loses to the Acreian Army and despite her struggles to survive in a male infested military, she is now about to die. But then, the young king of Acreia sees her efforts and tells her: "I have a dream, I wish to conquer the world and become an Emperor, would you like to join me?"

The King of Hell sentences you to death by midnight, but I can ensure that you live past morning.

The young man, Qin Lang, received the inheritance of a poison school by chance. He uses poison to kill people, uses poison to save people and he uses poison to chase beauties. With body of ancient extinct poison and a body of a martial artist, he walks around the city, and wanders around in the underworld.

- Description from Novelupdates

Every human on Earth was transformed into a summoned monster and was summoned to another world.