DéjàTale BACKSTORY: The player does not reset but instead did a genocide and loads the save file right before the sans fight every time they beat sans or loose to him over and over. But after so long the file space grows low... and the rest of the world is gone... leaving only the void, the judgment hall, sans, the player/frisk, and many, many, save files. NOW: Sans is still HP1 ATK1 DF1, but... if he dies... a file of him takes his place with all his memories of every battle and the one that just happened and continues it. NOTE: Sans, rather that remembering the resets or loads... simply gets strong Déjà vu of millions and more sans/past files of him, its so strong now that its basicly the same as remembering it and now shares memory with all the other versions of his own AU/past files. The sans's do not know how many resets/loads there have been, they can only guess by how destroyed the reality is and how he does in the OG game(frisk face).
Completely original idea, it may seem simular to others out there but it is a coincidence. PLEASE REMEMBER THIS IS A WIP.