UnderFell Sans X Reader

By UnderKillSans99

42.6K 691 490

MEH just another function ha ha a so hope you guys enjoy! (^v^)(^v^)(^v^) More

Part 1
Part 2
Part 4
Part 5
Part 6
Part 7

Part 3

6.1K 96 38
By UnderKillSans99

“Alright, we’re here.” Flowey lead Frisk to another wall that appeared to be solid but with cautious steps and her hands held out, she passed through. She was back in the ruins but was standing in front of that old familiar tree that stood in front of Toriel’s home. 

Flowey popped out at Frisk’s side and stared up at the home with painful memories.
“It doesn’t look like Toriel is back yet. Let’s hurry on through.” Scanning the area, Frisk confirmed it to be empty and proceeded to briskly walk up to the front door. Trying the handle, the door swung open and warm air filtered out. Frisk ushered Flowey inside before quickly closing it behind them.

Not wanting to waste time looking around, Frisk dropped down the stairs by twos and broke into a run down the long hallway. 
 As she rounded the last corner she stopped short to find Toriel had indeed been home and was waiting by the exit.

Hearing their approach, Toriel turned around to face the pair. “I had a feeling if I waited down here, you would eventually come.” Frisk tensed, ready for a fight but Toriel’s express was not aggressive.
“There is something… strange about you. For some reason, I feel like I know you… however…” Toriel’s eyes darkened and with no warning, she shot out a ball of fire. Taken aback, Frisk jumped out of the way as the fire burned dangerously close.
“I must stop you here.” 

“Mother… please. I just need to exit the ruins and find Sans. With his help, I can make everything right again.”

“Stop calling me mother!” Toriel yelled infuriated. “You are not my child and you will not leave this place!” A barrage of spells followed the fire balls and Frisk dodged around them, barely managing to keep out of danger. She was grateful that Undyne had taught her how to fight over the years or else she would have been obliterated by now.

“Don’t you understand, by passing through this door, you will be hurt far worse than if you just let me put you out of your misery.” 

“Mo… Toriel… this isn’t right. All the monsters had already left the underground… something happened and…” A pair of flashing orbs nearly caught her off guard but she dropped to the ground and grunted as she impacted the cold floor. 

“You stupid human, monsters can’t leave the underground. Don’t you think we were all sealed down her because of a reason?”

“It’s you who doesn’t understand. This isn’t real… none of it! Just let me finish talking!” Toriel let up on her attacks and glared at her with impatience. “Something happened… we were all in bed for the night when this light appeared and we all got sucked inside. After that, this world had changed. I don’t know how or why but I am going to fix it… if you would just let me try…” 

“How can I believe that… when all my memories are of nothing but pain and misery…?”

“Believe in me, like I believe in you!” With slow steps, Frisk crossed the space separating them and wrapped two gentle arms around Toriel. Toriel jumped stunned at the sudden embrace. 

“Let go of me. I don’t need your pity.” Pushing Frisk away, Toriel stood and turned her back to her. “Go then… and never come back…”

“Then..”

“I don’t know if I can believe your words, nor do I care. Just get out of here and try your luck on the other side. Don’t say I didn’t warn you…”

Flowey reached out a leaf towards Toriel as she walked past but her glare she cast him made him falter. 

“Don’t worry Asriel. I made you a promise remember. We are all returning to the surface as a family.” 

“Thanks and uh... can you just call me Flowey for now? It’s a little hard to be called by a name I abandoned a long time ago.”

“I understand. So… you ready? Cause… I’m still unsure as to what we’ll find on the other side.”

“It’s alright. I know this place like the end of my root. It’s not all bad, just the monsters living in it are…”

“I don’t know whether to laugh or cry at that comment…” Flowey gave a sad smile in understanding. 

Putting their weight up against the large double doors, Frisk and Flowey gave a heavy push, forcing the aged doors open. Immediately, a blast of cold air filtered the room. Shivering at the sudden drop in temperature, Frisk stepped through the large door before releasing it. With a loud slam, the door closed with a click. The passage was closed, she could only move forward from here.

“It’s really chilly up here. Do you mind if I borrow underground and follow underfoot?” Shaking her head, Flowey dropped below the floor, disappearing from sight. 

Taking heavy footsteps, Frisk crunched through the snowy blizzard. It was a lot colder than she remembered. Pulling up her jacket around her neck and crossing her arms in front of her chest to keep warm, she carried onwards. Sans was definitely on her priority list but finding shelter was at the top for now. She walked briskly, hoping to reach Snowdin before she became an icicle however, as she drew near to the bridge, she noticed the bars were actually pulled together with little gaps. 

“Now what?” She puffed out with frustration.

“One sec…” A muffled voice called out from the snow. Frisk was pleasantly amazed when a large vine sprang up, picked her up off the ground and dropped her off on the other side.

“Thanks Flowey.” She hollered down at him. He didn’t respond but she assumed he heard and carried on walking. 

The longer she trudged through the snow without running into any monsters, the more restless she got. It was eerie quiet, besides the sounds of blasting winds. ‘Maybe they all sought shelter inside from the storm.’

Just as she had thought this, her body began to grow hot. Screaming in hysteria, Frisk was yanked into the air and flipped upside down. Feeling dizzy from the sudden movement, Frisk closed her eyes but the rushing blood didn’t help much. 

“Yo Brat!” A familiar and yet unfriendly voice droned out. 

“Sans!” Frisk called out relieved. Down below indeed stood Sans but like the others, his appearance was different. His eyes were red, he appeared to be sweating a lot, he had one gold tooth and he wore a thick fur jacket with black shorts and red sneakers.

“Wow… you actually sound excited to see me.”

“I’ve been looking for you.” She quickly responded.

“Why? And what are you doing around out here? Just hanging around?”

“I need to talk to you about what has happened to everyone.”

“What has happened to everyone? First of all brat, how do you know my name? Secondly, who gives a damn about the others.” Releasing his power, Frisk dropped to the ground head first. The snow cushioned the fall but she had still been a few good feet off the ground and the impact hurt like hell.

“You could have set me down gently…” Frisk snapped, rubbing her sore head.

Sans only shrugged off the comment and stared at her bored. 

“As for your questions, I know you from another timeline, something happened and all the monsters wound up back here after having escaped to the surface and … are you even listening? This is important!” 

“Wuzzat’, I seemed to have stopped caring.” Sans was looking elsewhere, with his hands tucked in his pockets and his shoulders sagged. Turning a glowing red eye in Frisk’s direction, Sans looked her up and down. “You know, it’s strange. I have two very intense feelings clashing right now. I am feeling a strong desire to protect you, while the other is screaming at me to kill you….”

“Um…” Frisk shifted uneasily. “Okay...”

“And can you guess which is winning?” With a devilish smile, Sans released his full power with no restraint or hesitation.

Frisk stepped back startled and with shaky hands reached up to touch her stomach which was oozing out a warm, sticky liquid. Shivering, Frisk looked down to find a bone sticking out of her body, piercing her all the way through. Coughing up blood, she stared blurred eyed at Sans, and stumbled backwards, trying her best to stay up on her feet. Her eyes came in and out of focus to see Flowey dart out of the earth with a panicked expression.

“Frisk?” He called out desperately. Slumping to the ground, Frisk closed her eyes.

Just before the hands of death closed in around her, she quickly reset back time. As she arrived back to just before Sans had stabbed her, she collapsed onto her knees, holding her stomach where the gaping hole had been just before. It still stung from the aftereffects.

“Wow, guess you really can’t die.” Frisk stumbled away frightened to find Sans standing next to her, with his right eye closed and smiling brightly like he hadn’t just tried to kill her.

“To bad.” Frisk flinched at the comment. “Relax Brat, I was only joking. Come on, we should probably get a move on.” Frisk refused to move. She now knew she couldn’t trust this other Sans. 

“Don’t worry. My desire to kill you has already been satisfied. And I forgot to mention that it was Toriel who asked me to kill you. She never mentioned how many times, so I would say I kept my promise.” He winked teasingly but the action only made her want to curse.

“Oh and I should also probably let you know my brother is patrolling the area right now and well, let’s just say he is an overly dramatic human hunting fanatic. If he spots you, you are as good as dead.”

“Papyrus?” Frisk gasped out.

“Man brat, how do I know you?” Sans offered out his hand to hoist her up but Frisk knocked the hand away and pushed herself up onto her feet.

“Dang… you’re guard is to secure. And here I thought I could zap you.” Dropping a concealed object from his hand, a thin board with a red button attached to it plopped into the snow. He didn’t bother to pick it back up but instead started pacing away. 

Out of the ground, Flowey stuck his head out and stared after him with a frown.
“See what I mean?” Flowey said down-heartedly.

“But even so, he does have an awareness of me, which is better than nothing…” Deciding she should follow Sans, Frisk jogged over to his side. He gave her a bored look before turning away. They walked in silence for a few, slowly making their way to Snowdin. Frisk shivered slightly from the chilly air but with a look around, she noticed the blizzard had already passed. Her encounter with Sans had made her completely forget she was even out in the cold. 

“Sans… is Papyrus really going to try and kill me…?” Frisk hesitantly asked.

“Yea, that’s what he does. Why?” Sans tone was less fierce from when he had first started talking to her but he still looked disinterested.

“The Papyrus I know could never hurt anything or anyone. He is a big softy who loves hugs and making puzzles, cooking pasta…”

“Look bra… human. I don’t know what world you come from, but down here, kindness doesn’t exist. Didn’t Toriel warn you about that, or at least didn’t that weed below your feet tell you.” 

Flowey pulled out of the ground with a scowl.
“She’s trying to change everything for the better jerk!” 

Sans turned one glowing red eye and an evil smirk in his direction and Flowey immediately disappeared out of view in fright. 

“So you’re trying to change things huh. Honestly, I can’t deny that I know you from somewhere, almost like a distance memory, and I also have a feeling that I should trust you…. So here’s the thing human brat, I’m going to protect you. I love making promises if asked of me because they always give you a reason to do things that you sometimes normally wouldn’t, it’s kind of thrilling but making promises myself I don’t normally do. This is a onetime deal. If it turns out you’re here to kill everyone, well a promise is a promise, I’ll hold to my word. I don’t really care either way. At least this will be a nice change for once to this bleak place.”

Just as he finished talking, his left eye immediately burned deep red, like before, Frisk was yanked into the air and thrown behind a boulder. Thankfully this time, she was upright and caught herself before she pummeled into the stone. She glared out from behind the rock but then realized why he had reacted as he had. From the other side was Papyrus treading towards Sans with a scowl. Across his left eye was a large crack in his skull and his teeth were sharpened to a point. He was dressed in black pants with a red belt, long red boots and a black spiked shirt. The only similarity was his usual red cape. 

“Sans! Where have you been? There was a human spotted exiting the ruins and we need to find it quickly before another monster gets to it first.”

“Just go right on ahead. I’m dead on my feet, so I won’t be able to lend a bone.”

“Ugh, have you at least seen it?” 

“Nah bro. If I did, she would be dead already. You know there is no way I would ever let her get passed me, so shouldn’t you be grateful that I didn’t run into her.” Frisk’s heart skipped a beat and sure enough, Sans caught her eye and smirked. That god damn… he was purposefully specifying her gender. Thankfully, Papyrus did not catch on.

“But all you do is tell crude jokes and wander around pranking any poor unsuspecting monsters that cross your path. I doubt you’ve ever even killed anyone before.”

“Hehe, you’re no better. All you do is obsess over humans, brag about how cool you are and pick pointless fights.”

“Ahh! I’ve been so busy arguing with you that I completely forgot about the human. Stop distracting me you useless prick.” Shoving Sans to the side, Papyrus marched away, all the while grumbling to himself.

Stepping out from her hiding place, she approached awkwardly. She had never seen the two brothers fight… it was kind of unsettling.

“Whelp, now that he’s gone…” Sans proceeded to walk forwards, shrugging off the insults like they didn’t even faze him. 

“That wasn’t like Papyrus at all…” She could still see his figure in the distance stomping the snow with each step. His back was turned to them and he didn’t even bother to look back at his brother.

“Whatever Papyrus you knew is long gone brat.”

“Can you stop that?” Stopping short, Frisk breathed out a breath of agitation.

“Stop what?” Bewildered, Sans turned his full attention to her.

“Stop calling me brat!” 

His eyes narrowed at the comment and a mischievous smirk settled in.
“Alright Brat, let’s have a chat. You snap at me and I snap at you back. A brats a brat, unless you prefer to be called a rat or a gnat. And to add to that, you are quite fat and those ideas are rather flat. And what are you looking at? You started this spat. ..” 

“AHHH, you are impossible…” Sans was over joyed at seeing Frisk melt down. She strode past him annoyed and he followed behind snickering. “Real cute rhyming…” She added sarcastically. 

Instead of responding, he used his power to knock her off her feet. With a yelp, she sat down in the snow and as Sans passed, he patted her head.

“Di-did you just…” Sans threw his head back and laughed. All anger dissipated and instead, Frisk couldn’t help laughing as well. Surprised, Sans fell silent and watched her amazed.

“Wow… never gotten anyone to ever laugh at my jokes before.” Sans expression turned soft with the comment and his smile was a genuine happy smile. Taken a-back, Frisk’s breath hitched in her throat. Her first thought was that she had never thought Sans as being cute… and of all things, this alternate version of himself… her second thought was… DAMN. Cutting the thoughts off short, she stood back up and gave his shoulder a gentle nudge.      (Before anyone asks, NO, this is not a Frisk x Sans fanfic… XD)

“You just need the right delivery is all.” Giving his best appreciative smile, he nudged her shoulder back. Trying to hide his embarrassment, Sans picked up the pace and kept his stare peeled to the distance. Glad to see Sans in a good mood, she followed closely behind with a grin. Now that she had Sans with her, she felt confident things were only going to be uphill from there.

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