Do You Have a System That Allows Me to Cultivate Immortality While He Has the Technology?

One day, a sea of ​​stars that tore apart the sky appeared in the sky for unknown reasons. The unknown fear descended and destroyed the civilization of the current world. After more than 200 years of hard work by the remaining humans, an extraordinary city named "Nine Heavens" was built. It carries the last fire of human civilization and survives the destruction of the chaotic star sea. One day, an expedition team went out and unearthed the remains of a young man who lived before the world was destroyed 200 years ago in the ruins of the world...