Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/5334896.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      Other
  Fandom:
      Undertale_(Video_Game)
  Relationship:
      Asriel_Dreemurr/Frisk
  Character:
      Asriel_Dreemurr, Frisk_(Undertale)
  Additional Tags:
      Asriel_and_Frisk_are_teenagers, Nonbinary_Frisk, Futanari, Sexting, Chara
      is_in_there_somewhere_if_you_squint, mentions_of_Sans_Papyrus_Toriel_and
      Asgore
  Series:
      Part 1 of Teenagers_Asriel_and_Frisk
  Stats:
      Published: 2015-12-02 Words: 2490
****** Siblings...right? ******
by Redawilo
Summary
     Asriel does something kinda dumb and then he and his sibling end up
     sexting each other.
Notes
     This started out as joke where I would write stupid, half-assed porn
     whenever Skype took it’s dear sweet time in sending my messages to
     friends. And then I got attached to this particular idea and had to
     make it an actual fic. Also this is the first time I’ve written
     anything that can even be remotely called “sexting” so I’m pretty
     sure I am bad at it.
     I’m so sorry Mother, I am a dirty, dirty sinner.
See the end of the work for more notes
It had been some years since Frisk had somehow managed to free everyone, and
even save Asriel. Nobody had asked how they had been able to pull that off;
nobody wanted to hear the answer, although a few people had a funny feeling
they already knew what it involved. There were times where if anybody caught
Frisk alone, they would find them staring off into the distance with a smile on
their face that would cause shivers to run down their spine. No one was
particularly worried, as Frisk always snapped back to their usual self if they
were disturbed in those moments. Aside from that, Frisk was still the same as
when they had first fallen into the Underground.
Asriel flopped onto his bed. He and the rest of the monsters had grown
accustomed to how human society worked. Everyone he knew had somehow found a
way to fit in, his mother being a teacher at a local grade school for example.
Speaking of his family Frisk had election to stay with Toriel, and as such
became somewhat of a sibling to Asriel. Toriel and Asgore hadn’t quite gotten
back together, but of course Asriel and Frisk got to see Asgore just about
anytime they wanted. And if they didn’t think anyone was looking, their parents
were inclined to holding hands. Both children had caught them doing so multiple
times, but neither ever disturbed them when they did.
At the moment, Frisk was staying over at Sans’s and Papyrus’s. They did so at
least one weekend a month, claiming the two skeletons to be like the older
brothers they had always wanted. Asriel glanced at Frisk’s empty bed on the
other side of the room. As close as he and Frisk were, and no matter how much
Frisk specified that the skeletons were just the older brothers they had always
wanted, Asriel couldn’t help but feel a little jealous. Frisk had never said
anything even close to him being “the twin brother they had always wanted”. He
let out a sigh. It wasn’t worth worrying over. Frisk loved him, and he knew it.
He shook his head to clear the intrusive thoughts he was sure had only been
brought on by his tiredness.
He pulled the blankets up to his chin and rolled onto his side, burying his
face into the pillow. It was already passed eleven and he had school tomorrow.
Sleeping should be the only thing he thought about.
At least, that’s what his mind was telling him he should be doing. In reality
he shifted uncomfortably a few times, but try as he might he couldn’t quite
will away the erection that his teenage hormones had decided to give him for no
reason. He wasn’t really in the mood to take care of it, but he knew he wasn’t
going to be able to get to sleep as long as it was present.
With a groan he rolled onto his other side and picked his phone up off the end
table beside his bed and flicked on the lamp. He kicked his blanket off and
snapped a picture of the half-hard tent in his pajamas. He sent it and a
message to Frisk that read “Being a boy sucks sometimes.” Expecting them to be
asleep by now he was about to get up and walk around the room a little when he
saw Frisk was already typing back to him.
“tell me about it, lol!” was the reply and half a second later a similar
picture of Frisk’s recognizable red-heart print pajama bottoms arrived.
Cheeks flushing just a little, Asriel couldn’t help the giggle that escaped his
lips. Despite growing up with them Asriel would still forget sometimes that
Frisk even had a penis. Setting his phone down again he swung his feet over the
edge of the bed and stood. He walked a couple of slow laps around the room,
thinking about the essay that had kept him up so late that he had to turn in
tomorrow. It worked, and by the time Asriel’s phone buzzed the offending
appendage had returned to its normal state.
He sat on the edge of his bed again and picked up his phone, wondering if
Toriel had heard him up so late and had sent him a message telling him to go to
bed. It wouldn’t have been the first time she had done so to either of her
children. After all she still loved texting a lot and would still send Sans
terrible puns even if they were right next to each other. For the record, doing
so only minimally softened the blow to everyone else as they all knew it had to
be something truly awful if Sans always had a fit of laughter.
It was another message from Frisk, of all things. Asriel opened it and he felt
his heart thump harshly a few times in his chest. He fumbled with his phone for
a moment before putting it back on the end table and getting comfortable on his
bed again. He pulled the blanket over his lap, trying to think of how he was
supposed to reply to Frisk’s question, and wondering if he could just ignore it
and play it off as having fallen asleep. Unfortunately for him, his erection
had already started to return so he couldn’t even make it a not-complete lie.
“want to see it?” had been what Frisk had asked him.
Eventually he picked up his phone with a shakier hand than he would have liked
to admit he had. He stared at the picture he had already received. It was
innocent enough, all things considered. It wasn’t the first time he had seen
Frisk’s clothed erection. They were both healthy, teenage penis-owners who
shared a room, after all. Incidental boners happened. He had even initiated the
whole thing. Looking at Frisk’s question again made him nervous. Frisk was his
sibling, right? Frisk regarded him in the same way they regarded Sans and
Papyrus, right? So why was he feeling so tempted by the question that might
have just been a joke? It was a joke, right? Surely it was! There were plenty
of boys at their school who would joke about showing each other their dicks all
the time! This was no different!
Or so he tried to convince himself, but he knew that if Frisk were making a
joke they would have made it more obvious. Against his better judgement
Asriel’s thumbs tapped over the small keyboard on the screen.
“If you want to.”
There. The ball was back in Frisk’s court, and if Frisk sent him a picture now
it wouldn’t be on Asriel. He waited, phone clutched in his still shaky hands,
wondering if Frisk would reply again. Did he want Frisk to reply again? If so,
what with? Asriel couldn’t tell if he wanted Frisk to laugh it off and tell him
to go to sleep or for them to –
His phone vibrated again.
“you don’t have to be so shy about it ;) if you want to see it, you should just
say so” Again Asriel’s heart thumped harshly in his chest, and another message
arrived. “i’ll let you off the hook this time”
He had no idea what Frisk meant by that, but before he could ask they answered
by sending another picture. The hammering of Asriel’s heart increased tenfold
at the sight of Frisk’s pajama bottoms and boxers having been pulled down just
enough to expose their erection. Asriel couldn’t deny it; he was ridiculously
turned on by the sight of his own sibling’s hard-on. Laying his phone on his
chest and laying down a bit more on the bed, Asriel’s cheeks flushed as he
hooked his thumbs into the waistbands of his own pants and underwear.
“What am I doing? We’re supposed to be siblings…” he whispered aloud as he
pulled them down to his mid-thighs, freeing his own penis from its constraints.
It was standing as tall and proud has he had ever seen it, and knowing that it
had been Frisk that had made it that way only flustered the young goat more.
Nervously he took a picture of it, briefly considered deleting the picture, and
quickly hit send before he could convince himself to do otherwise.
“wow you sent it before i got a chance to ask for it!”
Asriel blushed again. That’s right, Frisk hadn’t asked for it. Asriel had sent
that picture of his own accord. Wondering if Frisk was going to give him a hard
time for it, he waited. Frisk was going to laugh this whole thing off, right? A
minute slowly ticked by and nothing happened. Sadly the anticipation hadn’t
helped Asriel to be rid of his erection, and he set his phone on his chest
again and reached his shaking hand to it. It was a familiar touch, sure, but
the circumstances made it feel strange. Frisk had made him hard, and Frisk was
his sibling. Surely that guilt was supposed to make it easier to pull his hand
away! Yet instead when the image of Frisk’s own erection forced its way into
the front of Asriel’s mind his fingers were still lightly stroking himself.
His phone vibrated again. “send me a pic of your chest and i’ll send you one
back”
If Asriel were to ever recount what happened for any reason, he would say he
only replied after much contemplation. But in reality he did so without
hesitation. He stopped stroking himself and pulled his shirt off. He held his
phone out above him, staring hard at the screen as he tried to find a good
angle. He determined that in the terrible lighting that was his bedside lamp,
nothing was going to look amazing. So he just took a few pictures and sent the
one he thought looked best.
A few seconds later he got what he had been promised. Frisk had pulled their
shirt up to their collarbones, exposing their stomach and small breasts to the
camera. Asriel drew a few shaky breaths. Thoughts of licking Frisk’s small,
pert nipples intruded upon his mind. He hesitantly typed each letter out,
second-guessing how he should word his thoughts every step of the way, and
there was still time to stop this whole thing. Frisk was supposed to be his
sibling! He decided that he was already in too deeply not to hit reply though,
and his hand returned to his dick and stroked it slowly as he waited on Frisk.
“I really want to taste those right now.”
“guess i’ll have to play with them for you”
The answer had been almost immediate. Frisk didn’t need to send a picture for
Asriel’s mind to race and cause him to gasp, hand gripping tighter around
himself. He was starting to drip pre-cum, and he had to wonder briefly when the
last time he had been so hard so easily had been. He wasn’t going to last much
longer, that was for sure.
“Frisk, I’m so close.”
“me too”
Another picture, this time of Frisk’s erection dribbling into their hand as
they were stroking it. Asriel groaned, picking up the pace. He thought for a
moment that maybe he was being too loud and that Toriel could hear him. Surely
not, it was late and they were on opposite ends of the hallway. All the same
Asriel couldn’t help but feel he was being much noisier than usual. He swore he
could hear his panting echoing through the room.
“i wish i were there right now, i’d love to hear you moaning”
It briefly crossed Asriel mind to ask if Frisk were psychic. “I wish you were
here, too.”
“i want to touch you”
“Me too.”
“can i see your face?”
Asriel couldn’t be sure if the picture he took came out well at all. He was too
frantic to be able to finish to take more than one. Frisk didn’t seem to mind,
simply sending a quick “thanks”. Not setting his phone down, Asriel instead
flipped the camera from the front to the normal one again. He was certain it
would come out badly, but that didn’t mean he wasn’t going to try. A few
strokes later and he drew a sharp breath, his seed spilling from the tip of his
penis. His left hand fumbled to hit the camera’s button in time. After taking a
moment to come down from his climax, he noted that the somewhat blurry shot of
his semen sticking to his fingers and running down his erection wasn’t all that
bad. He hit send.
The reply he was greeted with a few moments later was Frisk’s own hand sticky
with cum. It looked like they had actually bothered to try and catch it. After
a few deep breaths and his penis having started to go limp again, Asriel began
to regret not doing the same. It was going to take more work to clean himself
up that it would for Frisk. He was about to sit up and grab a few tissues from
the box on his table when he got another message.
“clear your history and delete the pics you took. never know when sans’ll get a
hold of your phone”
“Thanks for reminding me.” Asriel replied, remembering that the skeleton liked
to swipe their phones if he got the chance and text embarrassing things to
their mother. Asriel brought up the options and was scrolling through them when
Frisk sent one last picture. Frisk’s still dirtied left hand was on their
chest, forming what Asriel assumed was supposed to be half a heart. Their shirt
and pants had not been put back in order yet, and they were smiling up at the
camera.
“next time i want to do this for real, and i want to suck you off”
Asriel blushed again. Frisk was his sibling, but he began to understand why
Frisk had never said anything about him being the twin they had always wanted.
He looked at his own sticky hand and at his furry torso. It was one of the
very, very few times in his life he wished his fur were short like a human’s.
Instead he cleaned his hand off first before using it to form the other half of
the heart and sent a picture.
“I just hope Mom doesn’t find out.”
“she won’t if you’re quiet”
“I’m not that loud!”
“not in my imagination”
“Go to sleep, Frisk.”
“only if you do”
“Good night.”
“sleep well, bro. i love you”
Asriel’s fingers halted for a moment, but only a moment. “I love you, too.” And
then he erased his message history with Frisk and quickly deleted all the
pictures he had just taken and received. Finally he put his phone away, turned
off his light, rolled onto his side again, and fell into a deep sleep.
End Notes
     Welp, my first fic on this site and it's THIS! Yep. I'm starting this
     account off with a bang!
     I like to think that Frisk has spent too much time around Sans and no
     longer capitalizes anything in their texts, but still uses proper
     spelling and grammar (and a little punctuation) because otherwise
     Toriel would have their head.
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