Difficult Love (An Undertale Fanfic) *Completed*

Chapter 17

~Author's POV~

**WARNING: This chapter contains sexual content. Reader discression is advised!**

Sans quickly leaves Toriel's house and heads towards the lake. After five minutes, the forest surrounding the lake is in view. He stops and takes a deep breath before continuing to walk towards it.
Just before he enters the small forest surrounding the lake, he hears a familiar voice yell his name.
"SAAAAANS!!"
Right as he turns around, he is tackled to the ground by a crushing hug from Frisk.
"Heheh, hey, can't breathe.." he strains out.
Frisk lets go of him and stands up, extending her hand to him.
He takes it, allowing her to help him stand.
"What's up?" he asks, trying to sound as normal as possible.
"Come with me." Frisk demands, grabbing his hand and pulling him along quickly.
"W-woah, where're we goin'?" He asks.
"My house," she states firmly.
Sans looks at her questioningly. "Why?"
"Tell you when we get there."
After about ten minutes of walking, they arrive at the two-story brick house that is Frisk's home. Frisk opens the door and drags Sans inside, closing the door behind them.
She then pulls him along again, heading up the stairs.
"Hey, where are we-"
"Shh, just be patient."
Frisk opens a door and pushes Sans in, walking in after him and closing the door. She stands in the doorway as he takes in the sights around him.
It of course doesn't take him long to realize that they are in Frisk's bedroom. He turns to her in shock.
"Why are we..in here..?"
Frisk lowers her head and sits down, patting the spot next to her. Sans hesitantly sits beside of her.
Frisk sighs before explaining herself.
"One of two things are going to happen..either we try that one thing and see if it works, or..we're going to lay here together until you return to normal. I'll let you choose which one, because I don't want you to be uncomfortable. But let me just say.." she looks up at him, tears slowly sliding down her face, "I don't care if it's selfish of me, I want you to stay human..to stay with me."
Sans' eyes widen a little before his expression softens.
"I didn't know you cared that much about me.." He admits.
Frisk nods, staring right into Sans' sparkling blue eyes.
Sans looks down for a moment before returning his gaze into Frisk's eyes. "If you want me to stay with me that badly, then we can try it. I just.." his words trail off as he averts his eyes from hers. "..I just don't want you to do something you'll regret."
"..Sans."
Frisk suddenly hugs Sans tightly, her head against his chest.
"I'd never regret it, because it's you. So.." she sits back before slowly leaning towards him, her warm lips brushing against his now cold ones.
"I want you to stay with me. So please, don't leave me.."
With that, she kisses him again.
They continue kissing, each kiss feeling more and more passionate.
Sans breaks the kiss to gently lower Frisk onto the bed. He positions his legs on both sides of her thighs.
"Are you completely sure about this?" He asks, the concern portrayed on his pale face.
Frisk smiles. "I'd run to the ends of the Earth if it means I could stay with you forever."
Sans smiles sweetly, leaning down and kissing her again.
He hesitantly pulls off her shirt, exposing her frilly pink bra and slightly tanned, smooth skin. He reaches down to touch her stomach.
He thinks to himself, "If this doesn't work..this could be the last time I'll actually be able to feel her skin. It's so soft.."
He leans down and kisses the center of her stomach, causing her to flinch.
He then quickly looks up at her, concerned. "Are you uncomfortable? Should I stop..?"
Frisk shakes her head. "No, it's just..you're getting colder.." she admits, looking sad.
"I'm sorry. Maybe we should stop."
"N-no! It's okay, I promise."
Sans looks at her, skeptical, but continues anyway. He leans down and gently bites down on her collar bone, causing Frisk to let out a small moan.
He kisses down from her neck to her pants line, skipping over her bra. Hesitantly, he unbuttons her jeans and pulls them down. He lets out a small chuckle, seeing that her panties matched her bra.
"Wh-what's funny?" Frisk asks, feeling embarrassed.
"Nothing, I just think it's adorable. Do you always match?"
Frisk's face turns a bright shade of red. "Sh-shut up.."
"Sorry. You really are adorable, though," he mutters before reaching to pull down her underwear as well.
"W-wait!" Frisk says, causing him to stop.
"Did you change your mind?" Sans asks.
"N-no, but..it's not fair that you still have all of your clothes on! Besides, we can't do it if you're not naked too, right?"
Sans blushes. "R-right.."
He sits up and takes off his jacket, throwing it on the floor. He then removes his shirt, exposing his chest. His skin is still noticeably there, however you can see his ribs. Frisk blushes even more at the sight of him shirtless.
Sans lays back to make it easier to remove his shorts, removing his boxers at the same time. Frisk notices his erection, which is rather large, but also very pale, almost completely see-through due to the spell wearing off.
Sans looks over at Frisk. "Better..?"
Frisk's face is cherry-red at this point.
"What's wrong..?" Sans asks. "A-are you okay?"
Frisk looks away and nods.
"Y-yeah, just a bit..embarrassed."
Sans lets out a chuckle before returning his attention to her panties. He pulls them off and then positions himself on top of her.
"Are you..completely sure about this? It's not too late to back out."
Frisk closes her eyes and takes a deep breath before looking into his eyes. "I'm sure about this."
Sans leans down and kisses her sweetly while simultaneously entering her.
She lets out a loud noise as he continues slowly thrusting into her.
"Am I hurting you..?" he asks, not wanting to cause any pain for her.
"N-no it..it just..hah~" she gasps loudly, causing Sans to worry even more. He pauses, peering down at Frisk's face. Her breathing is abnormal, and her expression is different from anything he had ever seen from her.
"Should I stop??"
"N-no..please.." she says, grabbing his hand and placing it on her chest. He feels her heart racing. When he looks at her, she smiles sweetly.
"I've never felt this way before. I'm not really sure why I feel this way. All I know is..I want you more. I don't want you to stop."
Sans' face heats up, something he hadn't felt in a while. They continue having sex, until Sans feels something strange.
His whole body heats up, even warmer than it had been when he was fully human. He begins to feel a tingling sensation and light pressure deep inside of him as his heart begins racing.
"S-Sans..I feel strange."
Sans notices Frisk emitting pleasureful noises more frequently. He wonders if she feels the same way as him.
Suddenly, she moans out his name rather loudly. He feels inside of her become tighter around him, causing him to flinch. It felt great, but the pressure inside of him had built up too much. He felt his member twitching inside of her, as the pressure was released. He tries his best to hold back his own pleasure-filled noises as a wonderful sensation takes over his body. Not long after, he removes himself from Frisk's body and lays beside of her. He stares up at the ceiling, taking in everything that had just happened..the wonderful feeling, Frisk's voice..
He wasn't really paying attention to anything else, until he heard Frisk yell.
"Sans, y-your body!!"
"Huh?"
He sits up abruptly and looks down at his body, which was giving off a faint glow. His temperature seemed to be getting cooler and his bones were becoming more visible.
"N-no..please tell me you aren't--"
"Shh, calm down.." Sans says, trying to reassure her. "Even if this is it, at least we shared this moment together..a moment that will stick with me forever."
He leans down and kisses Frisk sweetly once again. "I truly love you."
Frisk huggs him tightly. "I love you too, Sans. I really, really do."
Frisk had to close her eyes as a bright light flashed throughout her bedroom.
Hesitantly, she looks up to see his familiar face. His slightly long, snowy-white hair; his sapphire blue eyes; and his pale..skin. That familiar face of which she had gotten so used to.
"S-Sans..you.."
Sans looks at her surprised face before looking down at his body.
"I-It worked.." He looks up at Frisk again and exclaims, "It worked!" again, before hugging her tightly.
Frisk hugs him back gently.
They both lean back and smile at each other.
After a few moments, Frisk blushes profusely.
"What's wrong?" Sans asks, touching her cheek.
"W-We're still..naked.." she points out, looking away.
Sans' eyes widen as he covers her with the blanket.
"I'm sorry. I hope you're not uncomfortable around me, now."
"N-no, it's just..you're the first guy I've ever seen naked. Also the first person who's ever seen me naked.."
Sans smiles. "I'm glad I could be your first..for many things. But more than anything, I'm glad we can be together now."
Frisk huggs Sans again. They both decide to lay down, since it is now late. Frisk lays with her head on Sans' chest, feeling his heartbeat.
"You're warm again.." she mumbles.
Sans only smiles, wrapping his arms around Frisk. They both fell asleep, happy to be in each others' company.