MTL - He Holds a Rose from the Abyss - Chapter 23 Lattilu's gun

Liola—the best assassin in his world—has vowed to kill no more. He was being chased by an assassination organization when he accidentally dropped into a parallel universe: through a dimensional gate and into poor teenager Kaiser’s apartment. Instead of going to the government shelter for lost dimensional travelers, Liola and Kaiser wind up going to school together.

Liola has been trying his best to live the life of an ordinary person, but after certain things happen one after the other, he begins to realize that being an ordinary person could be harder than being an assassin.

In the tenth year after the new era, the world finally came to an end. Zhang Mu truefully waited for his death, but unexpectedly found that he had returned to ten years ago. With his memory about the future, he swore that he would change the calamitous history, saving the earth from being destroyed! Walking dead, zergs, evolvers, and various mutated animals… nothing can stop him! The first step is to retrieve his identity as an era merchant , then find all the treasures he can remember to enhance himself!

- Description from Novelupdates

Mana finally arrived in our world after being delayed for unknown reasons, causing the evolution of everything that had life.

Humans, plants, and monsters all evolved, ushering the planet into a new era in which old laws no longer applied and the only law in the world was the rule of the jungle, where the strong preyed on the weak.

It was a question of whether we, the 'rulers' of the land, would be able to maintain our position and adapt to whatever came after our planet's awakening, and if we did, was that the end?

Vainqueur Knightsbane is your average dragon: a giant, fire-breathing lizard who loves to take naps on his golden hoard, kidnap princesses for fun, and make the life of adventurers miserable. Vainqueur's only pleasure in life is to watch his treasure get bigger, one coin at a time.

So when a would-be thief turned unwilling minion tells him about "classes," "levels," and "quests," Vainqueur wonders if maybe, just maybe, he should consider a career change.

After all, why bother hunting monsters for free when you can get paid for it?