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

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Groaning, Sans turned onto his side, facing his back towards the back of the couch, as he sleepily blinked open his eyes. Oh yeah, he was sleeping on Gaster's couch... He had come back here, after spending time with Papyrus and Mettaton at the park, while they kept his son entertained, and he even spoke to Kai for a bit - Frisk's friend. Admittedly, it had felt somewhat strange, talking to one of Frisk's friends, when he and her were no longer together. Hell, he even said that, and she simply stated that he was her friend too. To tell the truth, he didn't even know they were friends. But it earned a tiny smile from him to hear that.

After having blinked open his eye sockets, Sans couldn't help but tiredly raise a brow, noticing someone was lying on the carpet, next to the couch, beneath a large duvet with their head resting on a pillow. It was Leo. What in the world was he doing down there? "hey, leo..." Sans decided to reach down for him, and gently shake him awake. The 6 year old didn't respond for a couple of seconds, at least until he too began to groan, not seeming to want to wake up. "hey, what are ya doin' on the floor?" He asked. After all, he had been using the spare room upstairs, that Grillby and Gaster had offered to him, so he questioned why he wasn't using it.

"I couldn't sleep..." Leo quietly said, as he went to sit up and rub his sockets with a bit of a frown. He had been having nightmares, and they scared him so much that he couldn't sleep upstairs, in the darkness, all alone. So, he wanted to join his dad downstairs. He would have climbed upon the couch to join him; there wasn't enough space. Not wanting to wake his father, (as he knew how exhausted he likely was), he decided to lie down on the floor instead, finding enough comfort in that, knowing that his dad was right next to him if he needed him. Sans sighed.

"ya should have woke me... i'm sure the floor ain't that comfortable." He said. "...c'mere." He shifted a little on the couch, trying to offer any bit of space that he could to Leo, so the small boy could lie down on the couch with him. Leo paused, until he got up off of the floor, and he went to join his dad, sitting down in the small space that was provided to him. Surprisingly, it was quite comfy, especially when his father wrapped his arms around him in a comforting fatherly hug, just to make sure he wouldn't fall off the couch, as they both led together. "is that more comfy?" 

"...Yeah..." Leo nodded, feeling thankful. Sans tiredly smiled.

"heh... good." He said, letting out a huge yawn, as it must have still been extremely early in the morning. That, or he hadn't had a decent enough sleep. That might explain why he was feeling sore all over, and why his eyesockets felt so heavy. "go back to sleep if ya want... we don't have to wake up yet." The dad offered, already seeming ready to close his own eyes to get some extra sleep. Admittedly, it was a little nicer, having his son's company. He cherished his children so much after all, so any moment that he got to spend with them meant a lot to him. Their company meant everything to him.

"Okay..." Leo said, until he fell quiet in Sans' hold, not really sure if he could fall back asleep. Not because he wasn't tired; he was. Just... He had things on his mind. "...I miss mom." Leo admitted quietly. He could have sworn when he said that, he felt Sans' hold on him tighten a little - not that it hurt, but just that it was a noticeable difference. "I m-mean..." Leo started, as if he was going to take back what he said, because he knew what he said must have gotten to Sans, as he likely missed her a lot too. 

"...me too." Sans admitted. "do ya wanna go home?" Sans questioned. Because he knew that if Leo wanted to be with his mom, then he would gladly take him to her. He wanted Leo to be happy and comfortable, and if being with his mom is what he wanted... "because i can take ya home if ya want." 

"I don't know... I'm still mad at mommy." Leo admitted. "And I'm a little scared she'll be angry at me too... But I want to see her." 

"mommy won't be mad at ya, leo. she could never be mad at ya." Sans weakly smiled, going to lightly kiss Leo on his head as he continued holding him. He knew if anything, Frisk was likely missing their son like there was no tomorrow, and  that's why he had felt partly guilty about taking Leo with him. He had wanted Leo to stay with her, but when the boy had refused to stay, he had no choice but to bring him along. Sans didn't hate Frisk, even if he was angry with her. He still adored her, and he didn't want to wish bad things upon her as a result of his own rage. "she'd be happy to see ya..." 

"...Can we go see her then? When we wake up again?" Leo questioned. To tell the truth, it made Sans a little uneasy, knowing he would be face to face with Frisk again, so soon after their break up. But, again, he wanted his son's happiness more than anything, so if it was what he wanted and it might help him cheer up a little, then he would take him to Frisk. When Sans agreed with yet another tired yawn, Leo's smile widened. "Thank you, dad." 

"it's okay, leo..." Sans murmured. "now come on, get some extra sleep, before we go see your mother..." Sans told him, and Leo simply nodded, going to join his dad in closing his eyes so that they could get some extra sleep together. It meant a lot to the 6 year old, that his dad was putting aside his own discomfort to make him happy. Because as sad as it made Leo, he knew that his mom and dad weren't getting along at the moment. He hoped they would again soon though. Maybe this visit would give them the opportunity to talk too.

For a couple more hours, the father and son slept fairly peacefully. Well, as peacefully as they could. Sans was admittedly put slightly on edge at the thought of seeing Frisk again so soon, because he didn't even know what to say to her when he saw her. He was worried about snapping at her again over something, and the last thing he wanted to do was lash out again, and cause himself to lose her forever. He wanted to fix things with her, he truly and honestly did. But right now, it felt too soon. He felt like his visit to hand Leo over to Frisk was going to be extremely brief, because he wasn't sure he could talk things out right now. 

When they had gotten some extra sleep, the pair woke up to the smell of cooked breakfast, seeming to waft from the kitchen. Sleepily, Leo went to get up first, before Sans went to sit up, only to raise his eyebrows a little when he noticed Gaster standing in the doorway. He had been smiling, clearly finding it adorable how peaceful Sans and Leo looked, while Sans had been holding his son close, as if to protect him. "Had a nice sleep?" Gaster chuckled. 

"yeah... is that food i smell? smells good." Sans grinned in return, and Gaster nodded, mentioning how Grillby had started preparing something to eat when they both came downstairs to find Sans and Leo still asleep. "me and leo will have to leave after breakfast though... i'm droppin' him off at frisk's." He mentioned, seeing Gaster look surprised. Again, Sans didn't know if he was going to be able to talk to Frisk about their problem at the moment, so the visit from him might not be that long. But this was for Leo. His discomfort didn't matter, if Leo was happy.

"Okay, well, we'd hate to let you go out on an empty stomach." Gaster mentioned, smiling at the two who looked like they were practically drooling at the idea of food. The skeleton motioned for them to sit at the table, so they could be served once the food was ready. Grillby was a good cook, so Sans actually really liked Grillby's cooking a lot. At least with that, he might feel a bit more positive, actually having had something good to eat. 

He just hoped he would be able to handle seeing Frisk today.