A returner's greatest ability is the knowledge they amassed in their quest to become stronger—in the case of Ilyin Gray, his knowledge is the cost incurred to come back to life. As a seemingly ordinary 19 year old college student, Ilyin one day finds his world of Arden on the brink of destruction, winds up in a mysterious tower called a "Grand Ark" designed to help save the planet, only to be prematurely kicked out with little to arm himself against the threat that plagued humanity... just to find himself 157 years in the future, after society had long since pushed back the otherworldly creatures. The words of a mysterious divine named Hela claim that he spent many years fighting a primordial darkness as her selected adherent, using her powers to constantly bring himself back to the version of him that first entered the Grand Ark. With every reset, his existence was wiped from history, leaving him a forgotten and unsung hero. But now, his contract has been nullified, leaving him on his last life. As a result, Ilyin is thrust back into the human world with none of his important memories intact, told only to "live a normal life". However, having returned 157 years after his memories cut off, Ilyin is left broken and confused. With everyone he's ever known long dead, he is forced to rely upon an unusual darkness within that eats away at his emotions in order to stay sane, all for the sake of reclaiming normalcy. However, as a new threat begins to sweep across Arden, he is forced to seek out the mysteries of his forgotten past and confront his deepest despairs in order to protect his final, fleeting life.