Akame ga Kill: Starting with Dual Kamui - Chapter 106: Slaying the Minister’s Lapdogs

This story is centered around the man named Yi Ji-Hyuk, who has spent 1000 years in a Medieval Western fantasy-like world before returning back to the modern-day Earth. When he returns, he finds that his home is facing monster threats, and that humans with superpowers have appeared to protect the innocent people of Earth.

A mysterious natural phenomenon caused the Earth to be plunged into darkness. The world turned into an endless bloody chaos and mankind is on the brink of extinction…

Chu Yun Sheng, an ordinary white-collar worker, discovered his family heirloom book shining a bizarre light by accident. Out of curiosity, he tried to study the heirloom book.

After a long research, he still only understood a few symbols written in the ancient book. However, he was shocked when he figured out what messages the ancient book tried to tell him: the sun will disappear, and humanity is doomed…

He tried to spread the message, but no one believed him; his family and friends even tried to take him to see the psychiatrist. Eventually, he gave up telling anyone, but prepared for the apocalypse in secret.

Until one day– the sun really disappeared…

- Description from Novelupdates

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.

After an ominous prophesy is discovered, the swordsmen of the kingdom of Ensis must band together to avoid the fate that has already been foretold.