"This is important business today, okay? You'll have to concentrate on the meeting. Think you're up for it?" The elder brother placed his hand on Sans' shoulder, kneeling down to meet his eyes.
"Gaster! We're already here! I already told you, I want to take notes!" Sans piped up, rocking onto his toes. He was a big kid already, and he could handle responsibility!
"I know, kiddo. I just wanted to be sure." Gaster returned to his feet, and continued down the castle corridor. Sans had to jog to keep up with his eldest brother who walked with ease through a maze of extravagant halls. It was Sans' first time in the castle, and the views of the capital were incredible. He found himself drawn to the unfamiliar sites, before realizing his brother was turning yet another corner. The capital felt like a different world compared to Gaster's laboratory. Was this really the kind of world Papyrus lived in? Sans snuck glances down every hall, trying to absorb the royal atmosphere.
Gaster led him into a large room filled with a long table surrounding with plush seats. Unexpectedly, all of the seats were empty except for one, occupied by an older cat-man. "Finally, someone's arrived! I was beginning to think this meeting had been cancelled."
"Dr. Felix, its good to see you again. Where are the others?" Gaster helped the older man out of his chair.
"No clue. I haven't seen anyone else."
"King Asgore must have taken them off for a walk again. Could he arrive on time for once?" Gaster grumbled, then turned to Sans. "Stay here, okay? I'll go herd the others with Dr. Felix. Call me if I take too long. I might just need the interruption to get out of one of the King's rambling stories."
"You can count on me, Gaster!" Sans beamed, saluting his brother. Gaster smiled, and walked off with Dr. Felix. Sans took his messenger bag off of his shoulder, spreading the notebooks and schematic out on the table. He plopped down in one of the chairs, sinking slightly into the plush. Much more comfortable than the metal stools they had back at the lab. The castle was so fancy compared to home.
Tired of sitting, Sans poked around the room. Tall vases stood in each corner, full of some weird plant. It looked a little bit like a hotdog, and Sans wondered what it would taste like. Scientific inquiry! Gaster would say, but Sans didn't feel like testing out that hypothesis. The long table was intricately carved with floral designs, and Sans enjoyed crawling underneath it. Maybe he could pop out and scare Gaster when he came back! Sans giggled to himself, and crawled up to the edge of the table.
A burst of laughter echoed from down the hallway. It didn't sound like any of the adults that Gaster usually talked to. It sounded like they were children, around his age! Sans hopped up, banging his head on the edge of the table. He stumbled to his feet and followed the sound of voices, turning down an unfamiliar hallway. He peeked his head around the doorframe, and two children, a little older than him, were wrestling on the floor. The younger, a goat monster, laughed as the older pinned them down, tickling. Sans didn't know what kind of monster the older one was, but he felt embarrassed watching them. He ducked back around the wall, listening as the pair continued.
"Chara!" The younger coughed out. "Stop it!"
"Hmm? I thought you wanted to play with me, Asriel."
Asriel snorted before responding, "Monsters and humans! I wanted to play monsters and humans!"
"Well, I'm the human and you're the monster."
"You know that isn't how the game goes!"
More scuffling noises ensued, before Sans heard the two panting. They were having so much fun! He wished he could join them, but he couldn't push himself to walk through the doorway. What would he say to them? Sans never spent time around anyone in his age group. He hadn't even heard of this monsters and humans game the children spoke of! It was hopeless! He could never keep up with the people in the capital.
Asriel and Chara began to speak once more, distracting Sans from his turmoil. "I have to study my books now, Asriel. You understand, right?"
"But I want to play!" Asriel whined.
"We can't keep playing forever. You'll grow up like me one day, and everything will make more sense."
"You're not that much older than me!"
"It's different for us, you know that. Do all monsters mature at the same rate?"
"Well, no, but…"
"I'm going to join Mom and Dad with government duties soon, so I have to study monster history. They didn't teach this in my school, you know."
Asriel sighed, and Sans could hear him walking towards the door. He scooted further down the wall, ready to run.
"Asriel." The footsteps halted. "Do you want to play after I'm finished reading?"
"Of course!"
"Stay safe."
"Chara! I'm just going to walk around the castle!"
"Hey, let me worry about you sometimes. It's what older siblings do."
"You're not older-"
"Bye Asriel." Sans heard Asriel's footsteps once more, so he snuck back to the conference room, making sure to stay out of sight. Plopping down into one of the large chairs, he wondered what it would be like to have someone like Asriel had Chara. Gaster was so old, he was like a father to Sans. And there was Papyrus… he was never around, always busy with the royal guard. Maybe they could become closer in the future, and the three of them could be together, like a real family. His phone began ringing, and Sans jumped at the sound. Gaster must have found where the others were! It was time to prove himself as a trustworthy assistant.
Gaster was called for a meeting after the royal children died. The castle was cold and empty, this time. No one laughed.
The snow was so cold compared to the unending heat of the Core's lava. Before, he would have thought himself lucky to find a job so quickly after moving to Snowdin. Now? He couldn't stop thinking that the person who had this job before him had disappeared.
Sans watched Gaster slip into the machine. There was an explosion. At some point, Sans passed out. When he regained consciousness, Gaster was gone. Their research was gone. Their belongings. Their photographs. The lab looked like it had just been built. Sans checked his messenger bag, which he had been wearing at the time of the accident. His notebooks were still intact, along with a few blueprints. Sans ran out of the lab, desperate for help.
The Core stood in one piece, and Sans quickly found one of the employees that maintained the power plant. They didn't recognize him. He begged for help to locate Gaster. They didn't know him. After his outburst, Sans was escorted from the Core. He was exiled from the only home he ever knew.
Sans made his way to the capital, asking everyone he saw for help. No one had ever heard of W. D. Gaster, the revolutionary scientist that built the Core. Sans only knew one person he could turn to.
He found Papyrus outside the royal barracks, lying against the building. He was dazed and lost, and his lieutenants had kicked him out. When Sans arrived, a crocodile guard explained that the lieutenants did not recognize their own boss. Sans couldn't understand why Papyrus was forgotten as well. He used his magic to take them as far away as possible, and they found a place to live in Snowdin.
On his long guard shifts, Sans put together what had happened after the accident. Gaster had disappeared from the memories of everyone except for himself. Sans and Papyrus had also disappeared from the memories of the others, presumably because they were too close to Gaster. With the removal of Gaster, Sans had no reason to work in the Core, and Papyrus wouldn't have met Asgore. They had been exiled from their old lives, and the two distant brothers had been forced together.
Papyrus wasn't doing well. He had forgotten about Gaster like the others, removing large portions of his memories. He slept most of the time, and when he was awake, he was aware there was something missing. Sans had never spent much time with Papyrus, but he knew he was in terrible pain. His brother was broken.
One time, when Sans thought Papyrus was asleep, he spoke to Gaster. He quietly whispered about the events of the past week, when he heard a scream of pain from Papyrus. He shot up from his bed, holding his skull in his hands.
"Gaster! I know that name! I know him! I know him! I – AAUUGHH – I know I remember! It hurts but its there, Sans! I'm – AAAAAAAAH – I'm slipping! I can feel it!"
"Just stay, still! It's going to be okay, Papyrus! Don't hurt yourself!"
"You don't understand Sans! You can never understand!"
"Please, calm down!"
"Sans, in case I lose it all this time, remember I'll always love you. Both of you. I'm so sorry." Papyrus shuddered, his bones rattling. Sans did his best to hug him, despite his older brother's overpowering size. He always wanted to be closer to Papyrus, but never like this. Never like this.
Digging through the blueprints in his messenger bag, Sans found a photo of Gaster and his fellow researchers. The wound was fresh again, and Sans finished none of his work that day.
Why couldn't the timeline reset a little earlier? Couldn't he see Gaster one more time? Couldn't he have one joy in this unending purgatory?
How ironic, that the one to finally kill him would be the child he was too afraid to speak to, so long ago. The universe was playing a cruel prank on him. Sans was sure of it.