Hey, all! Kris here. I know I haven't uploaded in a long time, but Undertale has stolen my heart, as well as Sans, and I had this idea for awhile now. Since Sans had knowledge of every RESET, with further research, I predict he would have discovered Frisk or Chara LOADING before too. Also, before you keep reading, this is a fic where Sans is wary of both Frisk and Chara, and doesn't realize Frisk is being possessed with each Genocide run. Enjoy! New chapters will be up soon! Reviews help a lot!

It had been a day like every other in the underground, or the latest reset of the underground, anyway. Birds were singing, flowers were blooming…

And sans had a really, really bad feeling about this.

Asleep in his room as always, his garbage tornado whirring peacefully in the background of his thoughts, he winced as a familiar phantom pain began to throb on his rib cage.

It was coming. The human. And this time? Sans knew it wasn't going to be pretty. The resets had come to him to strangely at first, so nerve wracking, so jarring, he felt sick each time he awoke anew in Snowdin, his head spinning, his heart drumming, wanting nothing more than to throw up his nonexistent guts on the carpet Papyrus so dutifully cleaned every morning.

But somehow, eventually, it got easier. And easier. Sans began to notice a pattern, and on some days, that pattern was strayed from. At first, he had become wary of humans. Ever since Asriel, humans were a touchy subject in the underground, and sometimes, even a mention of one caused hackles to rise, and fur to puff. However, the many monsters of his world seemed to relax after a long while, and a human wasn't seen for the next five or so years.

That was until, They came.

It all had happened so fast. Laughing at his jokes, clinging to Toriel like their life depended on it, finding a new purpose, determination, breaking the barrier, the sun, the stars… at long last, peace.

He figured all was well. His little brother was laughing and running through the surface with Undyne, training every day, getting stronger, living the life he always deserved, the life that Sans couldn't have ever given him without the human's assistance. Frisk as they were called, seemed happy as well. They lived with Toriel, went to school, and had Sans and the others as their most trusted friends. Family.

Nothing had fucked him up worse than the very first reset. He awoke to his familiar ratty couch in Snowdin, with Papyrus nagging about his socks on the floor, and the next minute he was screaming, sobbing, tearing at his chest and begging it to be real, to be anywhere but back here, and after hours of his worried brother consoling him, he had begun to feel something manifest in his soul that wasn't laziness for the first time in years. He had begun to feel hatred. Hatred for the fact that they were still stuck here, hatred for the fact that his brother had no recollection of the past timeline, and hatred for humans in general. Not just all humans, one human in particular.

"You had what you wanted…" he had snarled at the broken mirror in their bathroom, that Papyrus had shattered during one of his and Undynes "training exercises". "You had all of us… a home… a family… the barrier was broken… we gave you everything…" His eye began to blaze a bright blue. "So why weren't you satisfied? Why are we back here again?" He sent a blue bone flying until a massive hole was created in the wall, and he vowed that if he ever saw that human again, they would have a very, VERY bad time…

That of course, didn't last long. The second reset, things played out differently than he ever could have imagined. Awaiting the human's arrival at his usual spot, his eyes went wide as the air begun to feel different around him. Trusting his better judgment, with a zap he teleported to a higher vantage point, and watched in horror as Frisk- or whatever that freak was going by now- cut down a helpless vegetoid with a few well aimed slices of a knife, and a toothy, murderous grin shinning beneath their bangs. He felt his heart stop as he glanced over in horror at his brother marching down the monster's current path, his eyes glowing in pride over his latest trap.

Watching Papyrus die later on for the first time was the worst experience of his life. The way he still offered that… Thing mercy, even after they were the last creature to deserve it, it caused his heart to break. As the rampaging human had finally subsided, and Sans managed to get to where his brother was, it had been too late. He clutched the familiar red scarf close, and screamed, screamed and begged, and pounded with his fists upon the snow. They would pay, he vowed. They would pay.

Twenty or so resets later, Sans was tired.

He knew pretty much every outcome, and his laziness was due to a lot more than just apathy. He was terrified to live. Terrified to have to face another round of uncertainty, another round of playing guessing games. Mercy? Slaughter? It was different each time. This human, this Frisk… was toying with this world. Turning everyone's lives upside down each time they became bored, and for the sake of his brother, it took all he had not to cut down the human where they stood each time he met them at first.

The thirty first reset, and Sans was finished. Sick, and tired. He sat awake in his bed, and heard the sounds of Papyrus cooking downstairs. He narrowed his eye sockets, and a hateful grin spread across his face. This stopped here. He watched his brother nag and fuss over him as he lay on the couch when he finally decided to join him, and inside his soul, he felt himself grow with determination. Papyrus always complained about his being nothing but a lazy-bones...

Boy, was he about to be wrong yet.