I Rely On Killing Monsters To Extend My Longevity

Story:

"Only the chosen dead can get to this place, where killing monsters can be exchanged for longevity, thereby prolonging life! Qianye, a survivor of a deadly battle, finally returns to the mortal world, only to discover that the reward is 'longevity' has a time limit! When time runs out, Kyanye plunges back into this abandoned and creepy place! What are these monsters? Is the sudden surge of eternal sleep in the mortal world related to this place? Who else besides me was chosen? There is no time to think, death is coming…"