Sans is a MONSTER and not a HUMAN, so he doesn't follow HUMAN biology like a HUMAN skeleton. Same with Gaster and Papyrus.  

---------------------

Admittedly, Sans was finding himself growing nervous when he knew his father would be coming by today as, as Gaster had agreed, he would end up staying with him, Frisk and Papyrus for the last couple of weeks, just in case anything ended up happening earlier than expected, and it was freaking the skeleton the fuck out. He had been trying so hard not to think about how much time was passing, but when he didn't think about it for awhile, and then he did stop to think about it, it only made him have a holy shit moment at how much time had actually gone past. He had a month left, a god damn month, and he was panicking. And he was panicking alone. 

Only because he had said to Frisk who was actually home for the day, as she was given some time off to be able to look after Sans. She was thankful to her really sweet bosses who were being very kind and understanding when she had briefed them on the situation. Point was, the skeleton had said he wanted to try and nap to get some rest, but he couldn't sleep a wink. Only because he was really thinking how huge this situation was, and what he was going to go through. The closer and closer his due date got, the more fearful he became. He wanted to stop feeling scared, but he couldn't. He really couldn't. 

Gaster had the feeling that his son would be feeling nervous, when he had been getting ready to head on his way to Sans', Frisk's and Papyrus' home. He was actually waiting around in Grillby's bar, as Muffet was supposed to drive him to the location, seeing as Mettaton was busy with the CIA today, so he was unable to be of use. And when the spider had arrived to pick the skeleton up, the flame monster at least wanted to say bye to him, as he knew it would be at least a couple of weeks until they would next see each other. 

"Don't worry. I'll be back before you know it." Gaster was saying, as he stood up from his seat, while Grillby stepped out from behind his bar and walked up towards the skeleton, seeming ready to get quite close to him, but then he remembered that Muffet was at the door. The pair looked expectantly at the spider, who caught the hint and mentioned she would just be waiting outside for Gaster in the car. The skeleton let out a small chuckle while Grillby decided to gently pull him in for a kiss, and Gaster happily closed his eyes, kissing him in return.

"That doesn't mean I'm not allowed to miss you, idiot." Grillby answered back with a hint of blue blush across his cheeks, once he had pulled away from the kiss. The skeleton laughed quietly once more. "But take good care of Sans. And be sure to let us know what they decide to name them." Grillby mentioned, while Gaster nodded, saying he would do just that. That being said, the couple decided to share a  hug with one another, until the skeleton knew he really had to get going. Disappointed, Grillby did let go of his skeletal form and allowed him to go out of the door. Yep, he was definitely going to miss having him around for the next month. 

"Hehe, that took a little while, I'm hoping I wasn't interrupting too much." Muffet joked with a small, mischievous seeming giggle, while Gaster did furrow his brow a little and he managed to blush a tiny bit at such a comment, but he simply cleared his throat calmly and was back to his poker face in a matter of seconds. "Okay, get in. We'll be there in about an hour." She said, allowing the skeletal monster to get into the car, so he could be driven to his destination. He just hoped that Sans would really be okay with him likely crashing on their couch for the next month, as he knew having him around might only make him more and more anxious for what was to come. But he promised to take good care of Sans, and as his father he would do just that. 

Deciding that he wasn't able to sleep a single wink, Sans actually decided to pick himself out of bed, as he felt like if there was anything he needed to do right now, it was that he needed to clear his head. He wasn't doing himself much good freaking out whilst staring at the four walls of his and Frisk's bedroom, so maybe instead he should go for a walk. "hey, frisk?" Sans said, as he headed downstairs, and he found her at the table seeming to eat food. Papyrus wasn't home today as unlike Frisk he was actually at work, only because he proudly stated that he would keep earning money for them to live off of. Frisk would have stated that she was still getting paid despite the time off, as the time off was for family reasons. But she didn't want to take away from the joy that Papyrus appeared to get for wanting to help, and seeing as he seemed to like his job as he got to cook, she happily let him go to work. "i wanna go for a walk, by myself. i just... gotta clear my head." 

"Huh? Oh, okay, if that's what you want." Frisk beamed kindly at her boyfriend. "Make sure you stay safe though." Frisk told him, causing a small grin to creep across his mouth at her saying such a thing. He teasingly replied that: wasn't it his job to say such things to her? He was glad though that she didn't seem to hold him back from going out by himself though, as while he could sometimes be clingy, as of lately he had been finding himself just wanting to be alone more. It was just the way his mood was sometimes, it was nothing against Frisk or anything like that. Just that he needed his space, that's all; she seemed to gladly respect that. 

That being said, Sans made his way to the front door, going to step out once he opened it and he proceeded to close it behind him. It was then that he just shoved his hands into his pockets, (as he was wearing a dark blue hoodie with a grey shirt and long black trousers that had white lines down the sides). He tended to dress more casual when they lived around here, or just when he wasn't working. His two pupils stared down at the ground with every step he took, as he wasn't really sure where he was walking, or what he was doing. He just needed a minute to think to himself, to take a breather. That's all he needed.

After the hour long car drive, Gaster was glad when Muffet pulled up, only to say that they had arrived, pointing out the house they had stopped directly in front of. "Thank you, Muffet." Gaster said, as he climbed out and closed the car door. She simply started the car back up once he had gotten out, and drove off once more, leaving him alone on the sidewalk. Walking up the path, Gaster stared around the neighborhood, thinking about how friendly it looked; it was peaceful. Raising his skeletal hand, he brought it into a fist, only to knock on the door in a rhythmic fashion. He waited a couple of seconds, waiting for someone to answer the door, only to see the door suddenly fling open to Frisk. 

"Oh, Gaster, hello!" Frisk said chirpily, or at least as chirpy as she could manage. "Is Sans not with you?" She asked, seeming to lean slightly out of the doorway only to look around. Gaster rose a brow at the human, only to notice that she looked a little on edge. She allowed him in after looking around. "Would you like anything? I'm sure you're probably hungry after the journey." The human stated, already seeming ready to head towards the kitchen, but Gaster stopped her.

"Frisk, what's the matter? You seem... Off." The older man stated. "Why were you asking where Sans is? He isn't with you?" He asked. Frisk turned back towards him, placing her hands on her hips as she bit down on her bottom lip in what one could describe as worry. "Frisk?" He repeated, only for her to sigh.

"He went out for a walk, about half an hour ago. I expected him to be back at least by now, but he isn't. I know I'm probably worrying for nothing, but..." Frisk rambled on, talking quite quickly as it was obvious she was scared about Sans. She had wanted to allow him to go out alone knowing that he needed his time and space, and he had seemed in a strange mood which she thought the walk would fix. "He seemed afraid, and I was thinking he was going on a walk to really clear his mind, but he isn't back yet. I even tried calling him." 

"And?" Gaster asked.

"He won't answer." Frisk replied, putting her hands on her head as she seemed almost ready to cry.  He couldn't blame the human for being concerned; just hearing all that she said made him worried too. But there was really only one thing they could do, and that was going to look for him. The human just nodded, but she first decided to write out a note and left it on one of the kitchen counters in case Papyrus or even Sans came home when they were out and that was just to say that they were looking for him. "I'm not even sure of where he could be." Frisk sighed, as they were outside, looking around the neighborhood. 

"For all we know he might just be staying in one place, maybe he just decided to sit around and didn't answer your call because he wanted to be alone. It is a scary time for him right now." Gaster explained, understanding why Sans would be fearful. He had remembered when he had been with his wife - Lucida. When she was pregnant with their first, (that being Sans), she had been pretty scared herself. Though, despite that she had always put on a smile. He really did hope she was resting peacefully. "Let's just look around." 

One of the first places Frisk decided to suggest was that they should look around near her work place, to see if perhaps Sans wondered off and decided to stop there. But when poking her head inside the cafe, she didn't see him anywhere. When she asked Kai, she said she hadn't seen him either. Though, on her way out, Frisk told her not to mention it to Papyrus, as she didn't want him to worry while he was at work. So, he wasn't there then... 

Next, Frisk and Gaster decided to head to the nearest park, which appeared occupied by quite a couple of youngsters. Though, beside the park, there was actually a walk way that people could walk along, which had trees on either side of the pathway. And when walking down this path, Frisk was shocked to see that Sans was sitting down on the ground in front of one of the trees, but he wasn't alone. She could see him, glaring up at what appeared to be three other people... It was... Those fucking... It was the same three guys who they had dealt with in the cafe. Clenching her fists, Frisk narrowed her eyes as she knew she was ready to deal with these guys, whoever the hell they thought they were. 

Sans was seen going to stand up, seeming to yell at them, and Sans did take a swing for one of them, hitting them right across the face, but that only caused the other two to grab Sans by either arm and they forced his back harshly up against the tree. Admittedly, it did wind him a little, but he wasn't going to let that stop him as he was already ready to use one of his two feet to kick the guy back who he had just punched. Though, as he was about to do that, the man in front of him was suddenly shoved to the ground, by none other than Frisk. "frisk! dad!" Sans looked to the side to see an angry looking Gaster, who looked ready to smack the other two men's heads together. 

"Is someone asking for a death wish?" Gaster questioned, his two pupils blazing with fury. Just when you thought Gaster couldn't get any scarier when there was something he wanted to protect, he even flashed the two men a spooky looking smirk, which definitely added to the scare factor alongside those two angry eyes of his. "Because I can deliver that to you if you want?" This caused the two men to once again make a run for it after letting go of Sans. And just as Frisk appeared ready to stomp on the third man's head, he had quickly picked himself up, only to run away with the other two. 

"I hope you get the message this time!" Frisk shouted after them, only to look back at Sans who she wasted no time to pull into a tight hug. "You scared the living daylights out of me! Why didn't you answer your phone! Unlike you, I have a heart, are you trying to give me a heart attack?!" Frisk ranted at her boyfriend, who tightly hugged her in return. She exhaled. "I'm glad you're okay... You had me worried..." 

"i know... i'm sorry. i just... i was feelin' really spooked when i was thinkin' about how soon it all is until... y'know. and i guess i just freaked out a little and needed to be by myself." He confessed, staring over Frisk's shoulder sadly. He felt guilty for scaring her like that, but he had just really needed the space, that was all. "i won't do that again... thanks for, uh... bein' my hero, i guess." He teased, pulling away from the hug only to grin at her. "i probably would have been okay though. it's not like i haven't been in a ton of fights with people before." 

"You mean a skele-ton." Frisk pointed out, seeing Sans raise his eyebrows at her as she had pointed out the pun, but he did actually crack up with laughter, as did she, and Gaster just stood with a warm smile, glad that they were both okay. He simply stayed silent, not wanting to ruin the moment between the two. "But I'm making up for all those times you rescued me." She joked back, while Sans grinned. 

"heh... also, heya dad... sorry to probably give ya a bit of a scare with ya bein' here on the first day." Sans said.

"It's fine. We're just glad you're okay, Sans." Gaster said. "So, Papyrus cooks in a cafe now, does he? Can we go there to eat? After my journey, I am actually feeling quite famished." The skeleton stated, causing the other skeleton and the human to nod and smile at him.

"sounds good to me."