I Just Want to Become an Immortal, but I Am Forced to Save the World

Traveling through the world of immortality, I got a plug-in that can make me stronger by completing dungeons. As long as you brush the dungeon every day, you can obtain countless precious resources. With just a shake of your little hand, resources are at your fingertips. The condition for opening the resource copy actually requires me to save the world? The world behind the copy is a real world on the verge of destruction! ... I was the Mr. Assassin that she still remembers after thousands of years. I was her only salvation in her miserable childhood. I was once the strongest warrior of mankind, and I made a promise to save the world. ... In the end, I carried the name of salvation and saved countless worlds that were about to be destroyed. But at the beginning, I really just wanted to cultivate immortality in peace and find the road to immortality!