"Stay With Me"

By MaturePopcorn

Description: AU where Frisk was able to truly save Asriel. As a result, Asriel and Frisk live together like Chara and Asriel did once before. Only this time, brotherly feelings go a little further… Story takes place in the future when Frisk is around 18, Asriel is about the same age.

WARNING: Rated M for HOLY HOT DAMN that's a lot of sex. Sorry if you aren't into that, but… O_o It's happening, so… Don't like, GTFO. 3 If you flame the review section… You're gonna have a bad time. Also fair warning, a side ship of Toriel x Sans is gonna happen here, too… ^_^

Author's note: …You think this is a joke? Are you having a chuckle? Haha, very funny, I'M the one with a degree. hOi im Kisa, and I looove Undertale more than THE VERY AIR I BREATH. Just kidding (kinda). Undertale has basically got my heart twisted in all sorts of weird knot shapes, and it won't go away (not that I want it to ^_^) so I'm going to write what I've always wanted to happen and hope that one day, one update, it comes true (Yo! Get on that, Toby ^_^) So enjoy what is basically my life now~!

Much love,

~Kisa Alvarez

Chapter 1

Asriel awoke slowly, first opening his eyes halfway, then turning over to his right side just enough to see Frisk, his adopted brother, softly breathing. "He's so cute when he sleeps…" Asriel warmly thought to himself. He yawned, showing his fangs, and stretched, sitting up. Rubbing his eyes, he let his mind drift. "What day is today… Saturday? I think…? Awesome, a day to relax. What's for breakfast… Hmm…" He glanced over at Frisk as the human boy made a small squeaky noise in his sleep and rolled over. Asriel blushed and smiled slightly. "So calm… And peaceful…" He thought for a moment. "I should mess with him."

Asriel got up, stretching further, and walked quietly across the room to his human brother. He grinned to himself as he kneeled down to be face level with the sleeping boy. He thought about what he wanted to say, then leaned in close to Frisk's ear. "Frisk… Frisssk…" He whispered.

Frisk moaned softly in his sleep. "N-no… Sleepy… Too early for that… Asriel…" He rolled over and stopped talking. Asriel paused, tilting his head in confusion. "Too early for… 'that'? What is that?" Asriel narrowed his eyes and thought of a new thing to say very quickly. "Too early for whaaat, lovey?"

Frisk let out a sigh, which turned into a moan, which woke himself up accidentally. "W-wha…?"

"Shit! Ugh… I guess I'll have to wait. I'll get him drunk and ask him," Asriel thought mischievously. He smiled so wide his eyes closed. "Morning, sleepyhead! It's time to wake up!"

Frisk stared back with his almost-classic blank stare, before adding, "It's 7:00. On a Saturday." And before Asriel could respond, Frisk promptly fell right back asleep.

Asriel sighed amusedly. "Fine, fine… I'll eat breakfast without you then…"

Frisk mumbled something that sounded like, "cool don't care", and rolled over onto his side. Asriel ruffled his hair and left, heading down the hall to the living room.

A while later, after Toriel had made pancakes and eaten breakfast with Asriel, Frisk finally woke up for good and came down to eat. "Good morning…" he sleepily mumbled as he shuffled into the kitchen.

Asriel shot him an exasperated but loving look from in the living room. "Howdy…? It, uh… It's past noon, but that's cool. Morning it is."

Frisk giggled, a little more awake now. "Oops… Well, I guess it's your fault for not trying hard enough to wake me up."

Asriel feigned annoyance, retorting, "Do I have to dump water on you every morning…? I will do it." He grinned. "You missed breakfast by several hours, but Mom was gonna meet Sans at Grillby's soon. You wanna come?"

Frisk nodded. "Of course; I love Grillby's burgers." He stopped to yawn and rub his eyes. "L-lemme get ready…" Frisk left the room, and as soon as the bedroom door closed, Asriel got up and followed. He went in as Frisk was getting undressed, earning him an expecting look from the human.

"Sorry, forgot my…" Asriel froze, panicked. "Shit! I only wanted to see him undress…! I didn't even think of an excuse…!"

Frisk tilted his head in confusion. "Forgot your…?" he prompted.

Asriel was now sweating heavily. "U-uhhm, I, uh, forgot my… My…" He looked around, desperate to find something, ANYTHING he could just grab and leave. His eyes found something and he spoke without processing. "My pillow!"

…

A silence fell over the room. Frisk resumed his blank stare while Asriel died a little inside. Frisk looked at Asriel's bed awkwardly. "Your… Pillow…"

"I-in case, I, uh, TAKE A NAP at, uhm, Grillby's…?" Even he didn't sound sure anymore. He looked down, avoiding Frisk's gaze, his fur completely red. "I-I'll just, uh, grab it now…"

Those next 15 seconds were the longest of Asriel's life. As he walked out and closed the door behind him, his face still burning, Toriel walked by. "Are you and Frisk ready to go?"

Asriel nodded, still looking down. "Y-yup," he mumbled.

Toriel narrowed her gaze at her child. "Why do you have a pillow? And that expression…" Asriel panicked again, if only momentarily. "Are you two fighting again? You know I don't like it when you fight with your brother…"

Asriel sighed relief, shaking his head. "No, Mom, it was a, uh, joke."

Frisk's voice sounded through the door, adding, "A weirdly unfunny joke."

Toriel opened her mouth to speak, but Asriel beat her to it. "I'M GONNA start walking to Grillby's, I'll meet you guys there okay? Okay bye!" He rushed out the door, still carrying the pillow. A moment later, Frisk came out in new day clothes and smiled at Toriel. Toriel awkwardly smiled back, thinking, "Why do I have such strange children…?" She smiled at this. "Oh well; life is all the more fun this way." She followed Frisk out the door and headed towards Grillby's, Asriel quite a ways ahead now.

Upon arriving at Grillby's, Asriel found Sans already waiting at a booth. He quickly and wordlessly shuffled in and sat down, placing the pillow beside him and burying his face in a menu.

"Heya, kiddo. You seem a little… Off. Anything troubling you?"

Asriel looked up ever so slightly from the menu, blushing at the memory of only a few moments ago. "N-no…! Everything's, uh, fine…" He gave Sans an unconvincing half smile, but before he could respond Toriel and Frisk walked in. They joined Sans and Asriel, Frisk sitting awkwardly next to his brother and Toriel nuzzling up against her boyfriend.

"Hello, Sans~!" Toriel blushed lightly and scooted closer to Sans.

"Hi Tori, Frisk. How're you doing today? It's a beautiful day out. I was thinking that after this, we could take a walk around Snowdin. Maybe watch a movie at my place."

Toriel smiled. "Sure! Anything with you would be fun…"

Frisk rolled his eyes and Asriel feigned a moan of exasperation. Toriel always got like this around Sans. It came with having a brand new boyfriend around…

Frisk turned to looked at Asriel, staring for an uncomfortably long time. Asriel pretended not to notice at first, but started blushing after only five seconds and kicked his brother under the table. Frisk winced only momentarily, and resumed staring. The table was now silent, Sans and Toriel watching in confused amazement as Frisk stared down Asriel, who in turn pretended to study the menu with all his concentration. Finally, he couldn't take it anymore. He turned to Frisk, wide-eyed, about to ask what he was doing when Grillby came over.

"Hiya, Grillby. I'll have my usual." Asriel breathed a sigh of relief as Sans broke the horrible silence at last.

They all ordered and ate in relative peace for the rest of the meal, only breaking it to talk about going-ons in the Underground and surface; Papyrus's latest antics, Toriel's pay-raise at the school, and so on. When they finished, they walked all the way to the entrance to the Ruins and back, stopping at San's house for a movie.

Frisk yawned. At only 3:30 in the afternoon, he was already looking forward to bed. "I think I'll go home. You guys watch your movie without me."

Toriel sighed. "Alright, my child… But behave yourself. And Asriel… Why don't you go to? You can catch up on your reading… Or…" She trailed off, not sure how to finish her sentence.

Sans grinned. "I sense an ulterior motive…? Okay, Tori, alone time it is."

Asriel got the hint and nodded, heading for the door. Toriel went back to the kitchen to make popcorn, and Sans stopped Asriel at the door. "Hey bucko, you never answered me back there. What's up? Something troubling you?"

Asriel grinned nervously. "N-naah, just kinda… Tired. I don't feel very good either, I think I might be sick."

Sans looked thoroughly unconvinced. "Okay, well… At the very least, take this," he said, handing him an unmarked package from seemingly nowhere. "Open it when you get home, okay? You might need it."

Asriel blinked and said thanks, a little confused. The door had just closed and he was barely to the library when he started opening the box. Inside was a note:

I know what's really going on here, kiddo. Be safe.

-Sans

Under the note were three condoms and a bottle of lube. Asriel dropped the box, with its contents and covered his mouth, blushing. "Sans knows… Sans KNOWS! How could he possibly know…?! Have I been that obvious…?" He paused. "Maybe… Maybe he's right. I should just go for it… Sans wouldn't have given me this stuff if he didn't think I at least had a chance." He took a deep breath and picked up the box. He exhaled, opening his eyes. "I've just gotta stay determined…!"he said to himself, and hurried off towards the Ruins.

The house was silent when Asriel opened the front door. He placed the box on the dining table and went to the fridge, pouring himself a glass of milk. He sighed, leaning against the wall. "What should I say to him… Should I say anything at all…? M-maybe this can wait…" He shook his head. "No, this can't go on any longer! I have to tell him how I feel. Even if… What I really want doesn't happen. He at least needs to know." He didn't dare let himself think of what would happen if Frisk liked him back. The thought, while so blissful in his mind, seemed so unlikely in real life. "I… Don't get ahead of yourself, Asriel. Whatever happens, happens." He breathed out and walked into the living room.

Frisk was in the living room.

The box was in Frisk's hands.

Frisk was blushing.

Everything slowly went white as the floor rushed up to meet Asriel.

Asriel slowly woke up to Frisks face barely three feet away. He sat up too quickly, and immediately regretted it. The pain was unbearable, and Frisk gently pushed him back down onto the bed. "Don't move. You hit your head pretty hard, and you could really hurt yourself if you don't relax."

Asriel moaned. "Wha… What did I even do…?"

"You fell. You've been out for ten minutes."

Asriel blushed. "R-right, before that…" Suddenly everything came rushing to the front of his mind and he almost fainted again. "Aah… Aagh! Y-you…! Box!" His entire face turned red as he spotted the box still on the table. He flipped over, burying his face into the rug.

Frisk blushed. "Y-yeah… The box… Um, did Sans give you that?"

Asriel moaned what sounded like "Mm-hmm" and Frisk sighed. "Well… Do you? Do you like me that way…?"

Asriel whimpered softly. "Yes! I've always liked you! I… I want to be with you for the rest of our lives…!" All he could do was think the words he so desperately wanted to say. They stuck on his tongue, unable to come out. "F-Frisk…!" Then came the tears. His soft crying was just barely audible through the wool rug, and Frisk smiled softly, rubbing Asriel's back through his shirt.

"Asriel…"

Asriel sniffed and stopped crying, though barely. He turned back over and looked at the boy he loved, unable to stop blushing and whimpering at the same time. Frisk closed his eyes and leaned down, kissing Asriel on the tip of his snout. "I love you too," he whispered.

Asriel stopped whimpering, compensating with extra blushing. "F-Frisk…?"

Frisk just giggled, smiling happily. "I know I should have told you sooner… It was so obvious how you felt about me, but… I was still scared. Irrationally scared. So I confided in Sans, and… Well, I think that's why he gave that to you. He knew I would say yes."

Asriel absorbed all this, and took a deep, shaky breath. "S-so… We can be together…?"

Frisk laughed at this. "Of course, silly. Otherwise I wouldn't have kissed you."

Asriel blushed. "So…" He hesitated, unsure of what to say now. Thankfully, Frisk said it for him. "The box?" Asriel nodded.

Frisk blushed rather deeply. "Y-yeah… Um… Do you wanna, maybe… Go to our room?"

Asriel's heart skipped several beats and his stomach turned over in excitement, happiness, and love. He tried to say yes, but all that came out was an excited squeak. Frisk nodded and helped Asriel up, supporting him back to their room. The second the door was closed and locked, Frisk had already gotten his shirt off.

"F-Frisk!" Asriel stared at the human boy's body. His skin was smooth, hairless, and tan, and he was just slightly toned. Asriel could feel himself getting hard through his jeans as he fumbled to get his own shirt buttons undone. Frisk grabbed Asriel's hands, stopping him, and kissed him on his mouth. They were both a little startled at the sensation, but enjoyed it nonetheless. They released each other's hands, and Asriel's hands began wandering over Frisk's bare chest while Frisk unbuttoned the rest of Asriel's shirt. They broke the kiss only to slide Asriel's shirt completely off, and Frisk hastily unbuttoned his own pants. They resumed the kiss, only this time their hands began wandering to other places…

Asriel moaned softly as Frisk's hand slipped under his boxers and touched his manhood. They broke the kiss again as Frisk started jacking Asriel off, and after a few moments of nuzzling like this, Frisk brought his head down to Asriel's jeans. He took hand out only to unbutton and unzip them, pulling them down around Asriel's knees. He pulled his boxers back just enough for Asriel's eight inch cock to come out, along with his balls. Frisk inhaled sharply and felt his stomach flip in love and lust. He brought his head down to Asriel's tip and hesitated only a second before putting his tongue to it. Asriel immediately squirmed in the bed and moaned loudly, only encouraging Frisk to put more in his mouth. Before long, almost six inches were in Frisk; the tip hit the back of his throat, and he couldn't fit any more. Using his tongue to play with the most sensitive parts, he stared thrusting from his neck, up and down… Up and down… Asriel was panting heavily; it was all he could do to not cum immediately. He grabbed Frisk's jeans at his hips and pulled them down without bothering to unzip them. Frisk stopped sucking to pull his boxers down, revealing his almost six inch cock, before resuming his previous action. Jacking himself off while sucking Asriel, Frisk started moaning softly in pleasure.

"F-Frisk…"

Frisk made a sound that indicated 'no', and Asriel whimpered. "F-Frisk…! I… I'm…"

Frisk realised what Asriel was so concerned about and started sucking faster, going down so fast that he was starting to hurt the back of his throat. But he didn't care. The moans given off by Asriel, the body heat from his crotch… Everything made it worth it. He kept going, and eventually he heard the loudest moan yet, followed by a sharp intake of breath. He braced himself, and flinched slightly at the salty taste of cum as it hit the back of his tongue and dripped down his throat. Asriel kept cumming… And cumming… There was so much that it started overflowing out of Frisk's mouth, dripping onto Asriel's balls and Frisk's chest. Frisk then came as well, this time landing all over the bed and splattering onto Asriel's legs and boxers, which were still around his knees. Frisk came up far enough for Asriel's cock to come out of his mouth and collapsed, his head on the monster's chest. He panted heavily as he pressed his naked body as close to Asriel's as he could. They cuddled like this for several minutes before Asriel broke the long silence.

"That was… Fun."

Frisk snorted. "F-fun?" He laughed, adding, "Wait until we actually use the stuff in the box. And, uh… some other stuff…"

Asriel blushed. "'O-other stuff'?"

Frisk nodded. "You don't really think you're top, do you? I only went down on you tonight because I was horny. Just wait until next time…~" He grinned mischievously at this, and kissed Asriel's chest. Asriel closed his eyes and smiled. He was perfectly fine with being bottom. Especially because it meant Frisk got to have more fun, which made him happy.

He kissed the top of Frisk's head. "I love you…"

Frisk nuzzled his head deeper into Asriel's chest. "I love you too… Goodnight, lovey," he said with a deep yawn.

There was a silence. It stretched on for several minutes…

Asriel's eyes burst open. "Is that what the collar under your bed is for?!"

Author's note: Whelp. I did it. Undertale, minimum of 3,000 words. O_o IT IS DONE

…

…

…Except… Not really… Becaaause…! There shall be more chapters! In which collars are explored! And, y'know, anal and stuff… *trails off* and stuff… stuff *mumbles* ANYWAY yeah, I'm tired… Also, to Alex of coc: I APOLOGIZE! Lol I know it's a few days late, but here it is! The story I told you about! ^_^ Can't wait for you to read it :b