Wortenia Senki (WN) - Volume 1 Chapter 2 (Summoned to Another world) 1

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.

Distant green mountains, a remote village, an ordinary boy struggling to survive, whose mundane life transforms into the path of cultivation. Who is real, and who is fake? Who can accompany the bright moon to the end? The world of immortals begins from here.

The grandson of the richest person, is just this willful.He doesnt wanna just be a rich guy who spends money for living,At this time, he became a bodyguard of a Beautiful CEO,“Be your temporary boyfriend? Can, but...”“Just show me how can we make a deal, or in other words, what can you do for me?”

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