1/28/16 edit: I changed the summary of this thing again I'm sorry; I keep coming up with better ways to summarize it! This is the last time, I promise. (Also thanks for the reviews, favs, and follows. It means a lot to me and pushes me forward in writing this behemoth.)

Prologue

The first time Sans met Frisk, he was incredibly suspicious of her. She wasn't entirely like the other humans that had fallen. She was more fearful, smaller, almost…disturbed. The others that fell had no qualms with hurting other monsters, whether it was in self-defense or not. This one, Frisk, however, seemed to avoid bloodshed not out of kindness, but out of a cowardice that kept her from hurting others. At the time, Sans figured it was for the best. It was easier to have kept his promise to Toriel about protecting the human that way. But something about Frisk kept nagging at him.

She was however, maybe more genuine than he originally thought when she had agreed to play along with his wishes and let Papyrus "capture" her. Sans was only slightly surprised when Papyrus and Frisk became fast friends. Papyrus was a cool brother, (his favorite brother, he would always joke), and the human's companionship made his brother happy—maybe even happier than Sans had seen in a long while. When Frisk was able to tear down Undyne's gruff and murderous exterior, even in the face of possible death, Sans began to place a little more trust in her; he began to watch over and protect her more, not out of obligation but out of sincere care. She made his brother happy, she made Undyne happy, even Alphys, and Toriel, and deep down he knew that he was genuinely happy to have known her. She laughed at his jokes, no matter how obnoxious they seemed, and went along with his pranks, no matter how juvenile. If Sans would ever allow himself to admit it…she almost seemed like a member of the family as far as he was concerned.

But he still had that nagging feeling about her.

She was one of the select few who ever got to see his façade fall, if ever so slightly. Every timeline that reset had sent him further and further down the mindset that he should stop caring. Why form a connection with something that would never be? Why care about something that wouldn't even matter the next time the timeline restarted? Why put effort into anything if it would all be ripped away from you eventually? But Frisk was causing him to change. During the time that she had been around, the time skips had stopped and brought a certain tranquility to his life that he had long forgotten. It was at the same time, relieving and unnerving.

But what if SHE was the reason behind why time was restarting over and over again? Or at this point, the lack of time restarts? He wouldn't ask her; he would just accept it. If he tried to explain to the young child and ask her about it, he doubted she would understand and Sans was never one to go into deep and emotional subject matter. He couldn't stomach it. He hated how any sort of emotional connection with another made him feel so vulnerable. He liked to keep up his joking exterior; no one else should know the things he knew or the things he felt.

Frisk wanted to go home, that was what drove her through the underground, even if she was terrified. If it was her, Sans had thought, surely she would be allowed past Asgore. Surely her kind demeanor would convince Asgore that he didn't need her soul—that he could let her go free and she could find her way home, or room in her heart to stay.

Surely…

But Frisk couldn't fight the king, neither could she run from him; she was too cowardly. She was stuck taking slash after slash from Asgore's trident, screaming for someone to save her. When Sans made it to her, he found her being pierced by a grotesque monster over and over again with Asgore nowhere in sight. It was a horrifying sight to behold: a small human child, dripping with blood, impaled on a disgusting monsters' tendrils. The beast loomed over her, laughing maniacally and staring at the broken body with four large gleaming eyes. It was nothing Sans had ever seen and the creature emanated the most evil aura, taking sheer delight in the carnage. The large television screen perched on what appeared to be the monster's head flashed menacingly, and it rounded on Sans, letting out a high-pitched screeching laugh. Sans had sprung into action and blasted the beast away, if only temporarily, before cradling the small child in his arms as tears streamed from his eye sockets. Why couldn't he have gotten there sooner?

But something was wrong. He could hear the abhorrent creature behind him slither and writhe, no doubt recovering from its wounds, but Sans' gaze was locked onto Frisks'. Her eyes looked hollow, her face twisted into a disgusting smirk as her body lay mangled and bleeding . She had looked back at him, body twitching and her arm reach for something Sans couldn't see, and began laughing.

Petrified in fear from the visage before him, Sans could feel the beast's tendrils creep up behind him, engulfing him as it did to her too; he felt them dig into his very soul, watched as they pierced her chest, tearing her small body apart.

"See you soon…"

Was all he heard her harshly whisper before he was smothered in light.

It had taken Sans only a moment to have realized the timeline had reset when he woke up in his bed. He felt immediately panicked. Worry and loss consumed him. If time had been reset, did that mean that Frisk was lost as well? He didn't know what to think, but he immediately hid his thoughts and feelings when his brother Papyrus had burst into his room, shouting about human-hunting, as he had done in so many previous timelines.

Even though his memories were vague and fuzzy, he still knew the basics. The promise he made to Toriel, meeting Frisk, the horrible monster. He desperately hung onto those memories, telling himself that he would protect Frisk better this time around.

But the next time he saw her, there was something off. She had always been a quiet human, but when he had met her on the bridge again, he saw nothing in her eyes. Immediately, he was taken aback. Surely that wasn't Frisk…was it? His intuition told him to be fearful of the human, that there was something horribly off, but he wanted to believe it was the same child standing in front of him as before. Once again, he asked Frisk to play along to Papyrus' human-hunting antics. She wore no expression, and said nothing, but had nodded. He was chalking it up to the fact that her memories had been reset, just like everyone else's, and that the bitterness in her eyes was just the status quo, human, irrational fear of being in a new place.

He regretted not listening to his intuition.

She killed everything in her path. Papyrus, Undyne, Alphys, even Metatton, and worse, every monster she came across, no matter how innocent, she ruthlessly murdered. Wherever she went, a trail of destruction and bloodshed followed in her wake.

Frisk…

His rage boiled over. He had trusted her, welcomed her like a member of his own family, and now everyone he knew and loved had been destroyed. In the back of his mind, there was no question to him that Toriel was long since dead. She had probably been one of the first casualties of Frisk's murderous rampage. He missed his friends terribly. Even if the timeline could be reset, this was inexcusable and horrific. In his mind, he couldn't shake off the feeling of finality to the whole terrible situation. What if this was the timeline where everything went forward, never to be reset? What if this was the reason time kept leaping back? Had it been that way just so this destruction and chaos could be accomplished? It was irrational, but he felt his soul being crushed by the realization that this was the first time he had truly felt alone. He didn't allow himself to fathom why Frisk had chosen this path of violence. He didn't care. His anger and wrath drove him to seek her out. To destroy her. In that current timeline, he would have revenge for all of his friends and family.

He had met her that day in the judgement hall. A mix of dust and blood had caked onto her blue and magenta sweater, even in her hair, making her look far more terrifying than a normal human child ever should have. In her small hands, she held a blood-stained knife and around her neck a small pink locket-necklace. Sans had wondered what the body count had been up to while he had wallowed in his misery and wasted time. A pang of guilt ran through him as he began to think of all the times he spent with her in the past timeline. He held back tears as he stepped forward, ready to kill the small human he once called his closest friend.

She had a disgustingly self-satisfied smirk as she rushed forward, ready to plunge her knife through his skull.

But she never would; over and over again Sans would smash her into the walls, the ceiling, the floor, he used the giant monstrous skulls he summoned, the Gaster Blasters, and blasted her over and over again, he threw countless attacks against her, watched her get pummeled over and over again until the floor was coated in crimson. Sans' wicked grin never left his face, anger pouring out of him like a geyser. The kid could never get a hit on him—he was too quick and attacked at a pace she just couldn't follow. He would not let the murderer of his loved ones go so easily. When Frisks' body finally lay on the floor too exhausted from blood loss and pain, he noticed the wide, evil grin she wore on her face. That familiar white light enveloped Sans again as he realized that Frisk truly was the one controlling the resets.

She had reset them back to the beginning of their fight, to how both were before getting too exhausted or injured. And she would continue to reset each time Sans would beat her. He hurt her over and over again, he heard her bones crack and break, he heard her scream out again and again, he could almost hear her soul break, until finally…

She lay on the floor barely breathing. She couldn't move and her terrible smirk was finally off her face, replaced with a look of helplessness and pain; it bore a striking resemblance to the old Frisk. Before Sans could think that it was finally over, her body had let out a sickening shudder, and a disgusting black mass writhed and wriggled out of her chest, out of her soul and levitated into the air. She screamed, and for a moment, her body nearly looked like it would be ripped asunder by the vicious secretion that expulsed itself from the small child. Sans took a step back before leaping to action and trying to blast the black ooze out of the air, but it had quickly detached itself from Frisk and dodged in the air before splatting on the ground and beginning to form what seemed like the body of a small human child, but much more deformed...much more grotesque.

"What…are you?" Sans had asked the foul substance.

"It's Chara, you fool."

And then something clicked into place. It wasn't Frisk that had done all those terrible things, it was this creature…this Chara. His left eye burned a vicious blue color as he glared at the disturbing thing in front of him. Frisk was innocent, it had been this…thing all along… this thing must have taken control of Frisk and forced her to do those terrible things. Sans had to destroy it. Tired and exhausted, mentally and physically as he was, he struck out with the last bit of magic he had and blasted the Chara creature until it was nothing, not even dust.

It was over…

Sans collapsed to his knees, too tired to keep standing. He looked over at Frisks' small body; she looked as though she had stopped breathing. In a panic, he got up as fast as he could and ran over to her. She had still been breathing, and Sans picked up her fragile form and cradled her to his chest. She was so broken and beaten up, and it was all he could do to hold it together as she whispered how sorry she was, how she regretted everything, how she missed everyone. He had tried to comfort her, but when she realized who was holding her, she could not be consoled. Fear took her and she struggled, screaming and crying to get away from the skeleton. Sans tried desperately to keep her still, to keep anymore of her crimson blood from leaving her tiny body.

And then she reached her hand out as if to grasp something before Sans could stop her.

Once again he was bathed in light.

When Sans woke up in his bed with fuzzy memories, yet again, he knew that time was reset. He had only the vaguest of recollections of Frisk, the human, and their possessor, Chara, as well as the horrific murders of all of his friends; even though it was a blur, he could put what fragments he had together and paint a picture in his mind of the horrific atrocities that occurred. And once again, as in previous timelines, Papyrus burst into his room ranting about capturing a human, interrupting Sans' thoughts.

When he found Frisk for the third time, he was surprised at how open and happy the human seemed to be. He wondered how much she remembered if anything at all from the past timelines, but when he tried to ask her, she merely cocked her head and looked confused, saying that she didn't know what he was talking about and that her earliest memories were of when she woke up in a small gathering of flowers in the ruins. If she had truly forgotten everything, maybe she also had no recollection of how to reset the timelines, if she was the true culprit of the space-time resets. He was going to keep a closer eye on her this time. Nothing from the past would be repeated, he told himself.

Like in the timeline past, she became fast friends with Papyrus, Undyne, Alphys, and even Asgore. Unlike the other two time streams, she spared monsters not out of fear or cowardice, but out of genuine goodness from her heart. Sans, however, really did try his best at forgetting the past and what he had seen her do—rather, what he had seen Chara make her do, but somehow he always felt stiffer around her than he ever was. Whenever he went to look at her, instead of her smiling face, he would see Chara's wicked, vile smirk, and her clothes and body caked in the blood and dust of his fellow monsters. Sans forced himself to try to act like his normal, comical self around her, and he wondered if she could tell whether he was faking it. If she could, she never let it show; she was just as sincere and candid to him as all the others and always took the opportunity to hang around him. She talked about her "mother," Toriel from the ruins and why the only reason she had left such a wonderful person was because she heard how the monsters in the underground were secluded form the outside and how it wasn't fair and that maybe she and the King could work together to break the barrier and let everyone leave the underworld. Sans told her how ridiculous that was and asked why she would even want to go to the surface when everything she could want was down below. With a determined sparkle in her eyes, she had repeated that everyone deserved to live freely, not trapped in isolation and that if no one was going to take initiative, then she would.

And even after she had saved the underground and broken the barrier, even after all the good things she did in the current timeline, even after all the friends she had made and how well she seemed to fit in, even after the fact that he knew Chara was vanquished, even after the fact that he knew without memories she could never reset the time stream again,

Sans still had a nagging feeling about her…