MTL - Dimensional Invasion of the Real Earth - Chapter 76 77. The Demon Rat Rage

Calamity descends upon a a tranquil world in the black of night, transforming it into a death game! This a a true apocalypse, but this is not the end of humanity!

- Description from Novelupdates

A man who was once called the world’s strongest agent ended up becoming a teacher after his retirement, to train a new generation of agents. After many years of training his disciples, he was killed at the age of 60 by a secret organization’s ruse and was reincarnated in another world with his memories intact. Though he was surprised by the existence of magic and the strange species in that world, he quickly adapted to his condition as a newborn and took advantage of it. He acquired special magic and gained a massive amount of strength thanks to his rigorous discipline, in order to reach his goal: Resume his career as a teacher which he left halfway through in his previous life. This is the story of a man, who, based on the memories and the experiences of his previous life, became a teacher who travels through the world with his students.

Years ago, Earth was indoctrinated into the “System.”Earth was not the only place with the System, however. With the System came the other races, Invaders. The Invaders had one goal, to obtain ownership of this new habitable planet. This created a bloodbath, and for years the war raged.This didn't really have much to do with Derek. Derek was kind of a loner. Yeah, he enjoyed the occasional chat or drink with others, but he never stayed in one place too long or really got to know anybody new.Derek did happen to be rather strong. After the years of fighting monster and Invaders alone, he had become quite adept at surviving. One thing that helped keep him alive was his refusal to get involved with others. He rarely cooperated with teams.One day, Derek broke his rules and decided to lend some help, as the mission didn't seem too hard. He should have stuck to being alone.

A century after the Spirit Qi Awakening, the world enters a new era. Humans are able to absorb the world’s awakened spirit qi, allowing them to tread on a new path—spirit qi occupations!