In the distant future world, human technology has developed to the point where it can explore the endless universe.
Although human science and technology has developed rapidly, human beings have a fatal flaw, that is, their life span is only a few decades.
In the exploration of the universe, humans have not discovered the existence of extraterrestrial civilizations. On the contrary, during the exploration process, he discovered the existence of the legendary demon and other world.
However, these demons and otherworldly beings are just like ancient myths. Their lifespan can be as short as a thousand years or as long as eternal life. That's what humans dream of.
