New story, yay...
This was requested actually by Casw123 . And I can't find the other person who requested this. So if your reading this, pls tell me so I can credit you. There are so many comments in my stories and I know that I can't find the exact comment who suggested this.
Although I already had this idea in mind.

Warning like usual, typos are probably everywhere. And terrible upload schedule btw.
Of course artworks ain't mine unless I say so

This story starts in the beginning of the anime and I won't include the slime diaries here.
So that's it, here's the chapter.
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Its another genocide run. Another failed attempt to stop the rampaging genocidal toddler like always. It always is such an unfair fight!

The fight between them was certainly odd... It seemed off. Glitchy particles was everywhere in the corridor. Some surfaces even lost its texture packs. It was certainly an odd fight, nevertheless. The player didn't even say a single word throughout the entire fight. Frisk just had a simple eerie smile painted across their face with its red glowing eyes. Now Sans was holding his bleeding wound hearing odd peculiar voices..

"I'll wake up again as the same old me. Resets are bothersome. I just want these resets to stop and to be strong enough to defeat them... What even is the player's motive?" Sans thought to himself, feeling the pain gushing through his entire body, he has gone used to it by now. Another gibberish voice was heard Sans couldn't understand what it said nor he cared what it said. He just wanted this to be over with and to wake up once again on his bed, knowing he'll have to follow the script once again. It's an endless cycle or endless loop if you may, he doesn't know how much resets he already had experienced and went through. He just knows that he's sick and tired of it. I mean we can't really blame him for that. This imprisonment of his, being unable to escape. His soul yearning for freedom long gone.

It really sucks being able to remember, huh? Well it's wise being not too knowledgeable. Knowing sometimes can be a huge unbearable weight. 

This player, this current one was just plain cruel, definitely. That can't be denied. It already have done 19 genocide runs this is the 20th. It's something that lacks remorse and guilt, it's not even a human anymore nor it can be even called that no longer. This creature had already walked pass that limit and it cannot go back no more, it's too far in. For this vile creature, the path of atonement is long lost, not even a glimmer of light left. It finds joy and bliss in the suffering and murder of helpless monsters, twisted isn't it?

Soon his sight slowly fading into pitch black and the familiar sound of dusting soon came. He is loosing consciousness as he was holding his gaping wound, situated right around his chest. The last thing he saw was the player just slowly waking along the corridor with a knife in hand, just heading to where Asgore is. They were smiling as they do so even waving bye to Sans for a bit. As he closes his eyes something odd was happening he could tell the glitchy particles from earlier were multiplying, though he's too far done to do anything about it. The moment that his head already dusted he felt like he was was suddenly falling or something like that. Well everything just went black.
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(Sans Pov)
I can hear the sound of water dripping slowly. My mind is still fuzzy and my head still hurts. As I opened my eyes and looked around I knew I was somewhere else. "Where am I..?" I thought to myself. This isn't Undertale.. I've been at every part of Undertale and this isn't one of them.. I tried to recall what happened and found no answer for this strange phenomenon, although I remember what had happened.

Lost in my very own thoughts. I never noticed something was approaching me. Though when it hissed at me, I was immediately alerted. It was a snake like thing, it was huger than normal. Using my bone attacks I defeated it quite easily. Then after I defeated it a white orb thing showed up, it went to me. And i grabbed it out of curiosity, but it disappeared or something. I didn't know what it was but I decided to use check on myself, to somehow be able to piece some pieces together. Then saw it looking quite different.. Sure it had the usual check box but a bit different it had mana- or something like that and it wrote [Is currently very confused]. But there was another box, it was dubbed as a skill box, interestingly it was scrollable. I looked at the skill box and it had some skills there was Extra skill: Bones, Unique Skill: Gaster Blaster, Unique Skill: Check, Unique skill: Karmatic Retribution, Unique Skill: Soul Absorption, Unique Skill: Bad time Mode, Unique Skill:Telekinesis, Unique Skill: Time Stop, Extra Skill: Heal, then more. Upon looking closer I layed my eyes upon  the poison breath skill, isn't this the skill of the monster I just killed? For now I layed it off and looked to my surroundings.

The location I was in was a cave of some sort then suddenly 1 saw a blue circular thing in the distance. It was taking or devouring every plant I saw and ore. It was headed my direction and I was near a cliff or some sort. I tried to stop it but it.. When I caught it, the force made me fall back and fall into a set of stairs, we went tumbling down and ended up landing in a body of water.. I can't swim tho, neither does this thing since we both sunk. Then out of nowhere I think it it inhaled some air expelled it in high speeds and we began propelling in the water. I was holding onto it dearly making sure that I won't be falling off.

(Third person pov)
When they stumbled into land while hitting a barrier and the slime hurt itself but managed to heal instantly. Sans was a bit curious of this but payed no mind as he looked to the enormous dragon seemingly trapped in the barrier. It had plenty of scars, proof of the hardships and fights it went through. Although it was a wonder how did he ended up here, alone in these caverns. Sans can definitely tell that it is stong.

"Can you hear me? I know you two can hear me" the dragon says, seemingly unsurprised by the sudden appearance of the two. He can supposedly sense their arrival, perhaps?

"Well yeah i can" Sans says, noting that he is deeper dow the cave that is in. Although monsters definitely seem to be avoiding this place, maybe because because of the imposing figure trapped in here.

The slime seems to be moving as if attempting to talk or communicate and a mad wrinkle thing popped up in it. Looks like it can form some shapes. But it doesn't seem to be able to talk whatsoever. Although the dragon can definitely tell what's its trying to say as they were somewhat communicating, Sans can definitely tell that. They were talking to each other. His time as a judge and ability to tell facial expressions and movements very well, was a help in this.

"Very well, I shall grant you sight" The dragon says to the slime and then says that he has terms however, knowing that this is something that it is able to take advantage of. It then adds "When you gain sight, you must not fear me. Secondly, you must come to converse with me. A beneficial arrangement for you, is it not?"

"You see. I was sealed in this place 300 years ago. I had naught to do ever since, and its been incredibly tedious."The dragon says to the slime as he lowered his head seemingly a bit saddened by this

"Well poor you." Sans says looking side to side observing his surroundings a little more closely

"Other one. You can see me right? but I don't think you know what is the little one saying." The dragon says to Sans, noticing that he doesn't seem to butt in whenever the two are conversing with minds, although he seems quite lost at the topic.

"Yeah, but it seems you can read it's mind." Sans replies casually as he looked up at the dragon. Sans doesn't seem bothered by all of this.

"Oh? You managed to deduce that almost immediately." The dragon says nothing his little observations. Looking to the slime he picks the topic right back up and says "Well for you, there exists a skill magic perception. Can you use it? It allows you to sense the magicules around you."

Then the slime seemingly tried using it and it seemingly wound up successful since it was jumping around and it immediately went to a body of water to probably see itself.

"Well?" the dragon says. The slime approaches it and does a little bow to show some gratitude. Then when it looked up it seemingly got shocked and scared.

"Allow me to formally introduce myself. I am known as the Storm Dragon, Veldora. I count as one among the four True Dragons that exits in this world." Veldora says bursting in laughter when the laughter subsides he notices something and then says "You other one, you do not seem to fear me at all."

"Well you seem like a friendly guy" Sans says with a bit of a chuckle at the end as the slime looks at him somewhat worryingly.

"Hey, little one. You remember our agreement don't you?" The dragon says as he switches up the topic and lowers his head

The slime seems it's saying yes, although it's scared. It pardoned itself to leave by bowing a bit, but Veldora says "Hold it! This truly is a rare occurrence. Slime are usually in significant monsters incapable of thought, but you posses an ego... Are you unique? Beings that possess abnormal capabilities." Veldora says and the slime seems to converse. "I see you we're reincarnated. Are you too?" Veldora asks Sans and faces him

"Well I died before I got here so I guess yes?" Sans replies being unsure of his answer.

"The way you two came into this world is incredibly unusual" Veldora saysas he is seemingly in deep thought.

"Unusual?" Sans questions and probably alongside the slime, as he tilts his head a bit to the right.

"Occasionally, others do make their way here from other worlds. But you two mark the first that I've known that made it through reincarnation. Most cannot withstand the journey between worlds only as a soul." Veldora says whilst moving quite a lot during explaining.

Sans was about to say something but noticed the slime is currently saying something to Veldora, again conversing through the mind. "Yes, they are called otherworlders. I've heard that they acquire unique abilities on they're way to this world." Veldora says as he looked to the two while the slime was slowly backing a way

"I've got a question though. What are magicules?" Sans asks as it was mentioned earlier by Veldora and it is written in the check.

"Magicules are similiar to atoms and made up of spiritions. They are invisible to the naked human eye and despite having mass, do not normally interact with most types of physical matter and energy, although they are capable of doing so. In addition it is heavily influenced by the minds of living beings and is able to take on many different properties depending on the situation." Veldora explains

"And what is spiritions? You just mentioned that" Sans asks as means to get more information.

"Those are just sub-atomic particles, kind of like a neutron" Veldora answers

The slime says something to Veldora seemingly something about leaving. This made Veldora down, well he cant be blamed he's been alone here for so long already

"What? You're leaving already?" Veldora says sulking.

The slime tries to make him feel better seemingly saying that he will stay for a little while. While it was scratching its head.

"Is that so!? Then stay for as long as you like." Veldora says excitingly

The slime then asks something to Veldora, because of this he slipped into story time and told about how he was sealed in there. Veldora exclaimed how lonely he is, since he was trapped for 300 years without anyone who to talk to.  Because of this the slime wants to be friends with him.

"What!? A mere slime wants to be friends with me, the feared Storm Dragon? Veldora says exclaiming

"Sure, count me in" Sans says as the slime was scared an looked confusingly to Sans

"I wasn't saying I dont want to!" Veldora answers to the slime who probably said something.

The slime stuck out it's hand and so did Sans then Veldora stuck out its claws.

Then the two conversed again with minds making sans a bit confused but payed no mind to it, then the dragon says if they have a way of releasing him. Since the truth is he can't last for another 100 years.

The slime got an idea although it was not that okay. It was something that stumped the dragon. Although Sans couldn't tell what the slime said but he could tell it was not good. Veldora laughed and agreed with the plan he said being together is much better than alone.

"You two are talking again and im lost." Sans says scratching his head being confused since the two just seemingly left him out

"Oh! Sorry we were just talking about me getting into their stomach and if the the things go well i would be able to break free" Veldora says with excitement

"Good for you then!" Sans says placing his hands in his pockets

"What about let's see each other's as equals." Veldora says as Sans and the Slime nods and then he adds "Humans have a similar concept its called a family name. But the name I will give you will grant divine protection. Since both of you are still unnamed this will enter you to the rank of named monsters."

"Well buddy, his name is up to you" Sans says patting the slime and then adds "Also Veldora, just call me Sans. That's what I was called anyways"

"Looks like that name is very important to you, very well then" Veldora says

"Tempest you say, very well then from now I shall be called Veldora Tempest!" Veldora shouted out of joy "Ant to you I will grant you the name Rimuru Tempest! and your well Sans Tempest!.

Well that seems like it was a power up as his name was apparently engraved to his soul already. Afterwards Rimuru did what they plotted to do which was ro store Veldora in its stomach.

"Well we better get going then" Sans says

As such the two just sticked together and basically defeated enemies that they went across, and of course they were gathering more and more skills in doing so. They just went, it was basically survival of the fittest. If you don't fight, you die. Rimuru can only seem to get skills when it consumes it and definitely does not like it. Sans well unlike Rimuru, he definitely still needs to sleep, but not eat for some reason. Although how can he eat without opening his mouth for Rimuru it was a mystery considering he said that that he could eat. When they defeated a bat it allowed Rimuru to finally talk through the use of a skill.

"Finally I can talk.. Or something like that I don't really need to open my mouth tho." Rimuru says to Sans as they tested out the skill

"Well congrats, your not too blue anymore now that you can talk, that is. Well it's not to much of a bone I don't even open my mouth when I speak" Sans says sneaking in a little pun. Although Rimuru did not seem to notice it until 10 seconds later

"Now that you just mentioned it, you really don't open your mouth when you talk. How did I just notice that? Wait- did you just made a pun..?" Rimuru says as they just realized something

"Yep" Sans says casually as he stood up dusting his shorts

"Hah, I didn't even notice that" Rimuru says as they jumped off Sans's head and then adds "I've got a question, where did you use to live?"

"Live, huh? I lived underground in Mount Ebott" Sans says as he ponders a bit one what had happened there

"What's that? I lived in Japan, I was stabbed to death. Although I used to be human" Rimuru says as they moved along

"You used to be human? Well I have been and always been a monster anyways." Sans says while walking alongside Rimuru, as he got Rimuru a bit intrigued.

"Well Sans what di-" Rimuru says as they was cut off by Sans shushing them

"Someone is coming.." Sans says in a low voice. Then he drags Rimuru away to hide for a bit.

Just at that moment there were three people that went in the cave leaving the door wide open. With this chance they just snuck away and look to the outside, it was a sight to behold. Although the entire cavern seemed to be acting like a seal for Veldora. Since they really haven't seen the outside, it was a sight to behold. Especially for Sans who hasn't been in the surface for so long...

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Well that's it for the first chapter I do hope ya like it.

3000 Words

-ImN0body