There were times Sans was left alone at the house. But although Papyrus never liked the idea at first, he has learned to cope with the fact that his older brother could take care of himself, despite his lazy and irresponsible behaviour.
Of course, it took long ways before he decided to leave him alone at the house.
The first time he did, he thought that maybe Sans would finally be a bit responsible and make his own food. But boy, was he disappointed.
They're just lucky that they live near water.
Papyrus still doesn't understand how someone like his brother could burned a whole house down just by making some kool-aid.
Anyways, Papyrus grew more trust into Sans when he started his training with Undyne. But at times, the captain would make Papyrus' training harder than other days to the point he doesn't even have the strength to check on his brother and take a look at the damage he made until the next morning. It was like this for a while: Papyrus got up early in the morning, trained with Undyne the whole day, and then came back only to collapse on the couch. But he would always seem to wake up in the morning all snuggled up in his bed, occasionally seeing his smaller brother snuggling up to him as well.
It was then that Papyrus decided to have heated up spaghetti just for Sans for when he wakes up. He would often leave a note on the side that contained an apology for not checking up on him the night before. And for him to pick up his sock. He never really does though.
Anyway, Papyrus would occasionally stop the training to chat with the occasional monster that stopped by to see how he was doing. Undyne would often allow him to go off into the marsh with other monsters. Sure, Papyrus doesn't have a lot of friends, but it would be best if he could keep the ones he had at the time.
But one day, Papyrus had forgot to leave out some food for Sans. This was unusual since Papyrus always remembers everything that's important. So when he realized his mistake, the guilt overtook him. He was so close to breaking off into a sprint to the house but he was with the little monster kid and he didn't want to be rude by ditching the lizard child. So he excused himself and dashed back to Undyne.
"UNDYNE! I FORGOT TO LEAVE SOME FOOD FOR SANS.." He talked rather quickly, "COULD YOU RUN OVER TO GRILLBY'S AND PICK HIM UP A HAMBURGER? WE DON'T HAVE ANY SPAGHETTI AT THE HOUSE!" But before the fish could retort, the skeleton already shoved some gold into her hands and sent her off.
Undyne simply grumbled and went on her way, watching the skeleton run off with the child into a patch of echo flowers.
When she got to Snowdin, she wasn't shock to see everyone staring at her with big eyes. She was considered a heroine in the town so it was normal to be praised and looked up at.
Which was good because she got a hero's discount on the burger. She reminded herself to give the extra gold back to Papyrus.
Usually, when she visited the skeletons' home, it was very welcoming and warm. But today, it had a weird and creepy vibe to it. She sensed it as soon as she stepped into the large house.
The lights were off and the atmosphere was cold and dark, and not in the lighting kind of way.
"Sans?" She called out, setting the greasy food on the table, "Papyrus wanted me to bring you some grub. You here, nerd?"
She didn't get an answer, but she did hear a small, faint noise. Maybe a whimper? Now Undyne was curious.
She grabbed the to-go bag and walked up the stairs. The sounds of panting and whimpering got louder with every step she took. When she reached the top, she took noticed of the blue energy slipping out under the door of Sans' room and ran over to the bedroom door. What was he doing in there?
"Sans? You in there, dude-" She said as she opened the door.
The sight she was taking in was not expected at all; Sans was curled up on his bed, his bony hands clutching his head as if it was going to fall off. Large amounts of blue energy was escaping from his left eye and he was sobbing awfully loudly. All of this took Undyne by surprised.
She quickly set the bag of food down and ran to the short skeleton's side, "Dude, are you okay!? What's wrong!?" Only the skeleton didn't hear her. Well, it was more like he was too occupied to even care who saw him at this state at the moment.
The royal guard captain grabbed his shoulders and started to shake him a bit too harshly, "Snap out of it!" The skeleton brother only just sobbed louder, clutching his head even tighter.
Undyne, not sure what to do, quickly grabbed hold of Sans and pulled him in for an embrace. Now, this was very unusual and out-of-character for someone like Undyne but this was her last resort. And she has never seen Sans like this before. He was always such a chill dude. She could never expect something like this from him. Was he always like this when no one was around? Better question: WHY is he like this?
Everything seemed to freeze for Undyne as she tightened the grip. Sans had stopped sobbing. That's good. And the blue energy was started to fade. That's great.
But it was then that Sans actually hugged back. That's awesome.
"Sans. What the fuck happened to you?" She muttered out.
"u-undyne..?" She heard him say quietly. That was the first time he talked since all this.
Wait, did he not know this was her?
"What's up, nerd?"
"you're squeezing my ribs."
...
The silence became a clingy companion for the two as they sat awkwardly on the bed, waiting for one or the other to speak. But no one would dare to mutter a word for it would break the silence. And Sans was actually starting to like it. It was until Undyne spoke up.
"How often do these happen?"
Sans didn't want to answer, but knowing her, she's never going to quit unless she gets to the bottom of things. It's a determination thing.
"often. about once every other day."
"Does Papyrus know?"
"yeah. it's one of the main reasons he doesn't like me being home alone."
And there goes the silence again. Only this one was shorter. Undyne wanted to say something but it might be too personal. Oh well, might as well give it a shot.
"Why were you crying?"
Sans replied, but not right away, "nightmares. they happen every night."
"Is that why you sleep while you're on-"
"yeah."
Now it was Sans turn to ask a question, "what are you doing here?"
"Papyrus wanted me to bring you some food since he forgot to leave out some for ya." She smirked, "Though I wasn't expecting this."
"yeah." Sans chuckled slowly, "sorry about that."
"Don't sweat it."
Once again, they were swallowed up by the silence. Undyne has never been in such an awkward situation before. I mean, what are you suppose to do when someone who's known to be the most cool and chill guy in town breaks down right in front of you. Although Undyne was very curious about Sans' dreams and what they were about, she thought that he had enough for today. She stood up and walked over to the food bag, picking it up and handing it to him, "Got ya extra ketchup. The way you like it."
Sans smiled and took the food from her, "aw. you shouldn't have."
"Oh shut up, nerd." Undyne smirked and checked the time, "I got to check on Papyrus." She started to walk off before stopping herself, "Sans..."
He looked up at her.
"Look..." She rubbed the back of her neck, "If you need someone to talk to... I'll be there for you, little buddy... Stay determined, okay?" She suddenly ran out, leaving a smiling Sans behind.
"... kay."