Upon Returning Home As A Military Major General, I Was Told To Attend School, Even Though It's Quite Late Now - Chapter 12.2: Hayami-san’s Superiority

Forcefully brought over from the modern world to an alternate world, Wang Chong felt detached and lived his life aimlessly.

However, when calamity struck and he saw his family and everything he cared for being torn apart, he felt regret.

Thus, he stood up and eventually became the Grand Marshal of the Central Plains, leading an army against those who seek to destroy all he cherished.

Yet, despite all his efforts, it was already too late to reverse destiny.

But before his death, a shooting star, the same one which brought him to this world, appeared before him, and he was given another chance to undo his regrets.

- Description from Novelupdates

Naofumi Iwatani, an uncharismatic Otaku who spends his days on games and manga, suddenly finds himself summoned to a parallel universe! He discovers he is one of four heroes equipped with legendary weapons and tasked with saving the world from its prophesied destruction.

As the Shield Hero, the weakest of the heroes, all is not as it seems. Naofumi is soon alone, penniless, and betrayed. With no one to turn to, and nowhere to run, he is left with only his shield. Now, Naofumi must rise to become the legendary Shield Hero and save the world!

One day, I woke up only find out that I’d become a Demon Lord, an individual responsible for protecting a dungeon. The world I’d been spirited away to was one filled with violence. Gigantic monsters wandered through it and competed with each other each and every day for the right to survive. I had no choice but to strengthen my dungeon’s defenses in hopes of living another day—or at least that was what I’d thought. For some odd reason, I instead ended up spending my days in relaxation and bliss.

In the year 2220, a radiation source in the Pacific Ocean, tens of thousands of times stronger than a nuclear bomb has begun mutating exposed creatures into horrific monsters thousands of meters long. Mankind’s only hope was nuclear weapons, which only made matters worse. The combination of the natural radiation and nuclear radiation released an incurable and highly infectious virus, turning the 90% of the world’s population into violent zombies in mere weeks.