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

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

Leo would be lying if he said he wasn't scared. Because in all honesty: he was. No, the play that they were doing wasn't today, but it was very soon, and he was beginning to question whether or not he would be able to do this, even with his mom and dad still motivating him to do well. Mommy wasn't as home as often as she normally was, (even though she was normally quite busy anyway, she just seemed a little busier than usual lately), but when she was at home, she was continuing to give him the push to perform, alongside his dad. It did make it somewhat easier to calm down when he was given so much praise before he had even performed, especially when it was not only by his parents, but his sister, and his friend Kyle too.

Kyle had only been his friend for a couple of days, but he was already liking his company. Actually, Kyle was a latecomer into the class, and unlike everyone else, the young boy had warmed up to Leo quite quickly, and had wanted to help him build a tower out of blocks, (unlike that other kid that had tried to steal them from him). It had felt nice, to feel like for once he wasn't been totally judged in the classroom. That was the thing about being a small, 6 year old child - for some, it felt easier to form a friendship within the span of a couple of hours, because you weren't yet a teenager, or an adult who would likely have many trust issues due to the many friendships you would have already experienced, and they would have failed. 

They were just innocent kids, enjoying their time together. 

Because Kyle was a latecomer, he was placed into the play as just another angel - it meant he wouldn't really have to say anything, not that the child minded at all. He could relate to Leo on the level that he didn't really actually enjoy acting that much, not that he wasn't quite a bubbly child; he was. Playing pretend could be fun, when you were in your own little world and you didn't have to feel self conscious about people watching you. But the moment you were stood up in front of a bunch of staring eyes, it was easy to get stage fright. Leo's fear was that he would get stage fright, and that he might start crying like an idiot. 

"You will be good!" Kyle had told Leo, when they were in the classroom, deciding to build a tower of blocks together. Leo ended up smiling in gratitude towards his new found friend, who was clearly trying to be nice. "Your mommy and daddy will think so too." Kyle added, deciding to add another block to their tower. Yeah, Leo really hoped so. They seemed like they were already looking forward to it, and that was the main thing that was giving him the push despite him hating acting. 

That's what was weird about this, he was excited to perform, despite being scared and hating acting, because he preferred to just be in his own little world, where he didn't have to care about the judgement from others. Even at 6 years old, it was clear to him that people found it harder to take a liking to him because he was different; he didn't look like all the other kids. Even now, there were still no other children here who were a mix of both a human and a monster; they were either one or the other, never in between. It was a challenge not to feel different, or judged, when you knew you were very clearly the odd one out compared against everyone else. He knew he wasn't alone, that Luna was different too, but because she looked more human, and she had a more easier going personality, she had an easier time making friends.

The fact that Kyle even wanted to be his friend was surprising to him, because he was one of the first people the other boy had spoken to. He didn't quite understand it, maybe there would never be a time he would ever understand it. All he could think was that he was at least glad to have a friend, even if it was only one friend. 

"Yeah, I hope so." Leo beamed at Kyle's kind comment, before the two of them broke into conversation on how to construct the tower. Luna on the other hand was playing a game of puppets on the other side of the classroom - she had a puppet that looked like a princess, because it had a very pretty dress, and nice, long, red hair, with a little tiara. Luna loved how colourful and cute she looked. She was actually playing with a group of students in their class, and Luna had thought about asking her brother to come over and play; part of her thought he wouldn't want to though.

Still, at least he wasn't alone. It brought a small smile to the sister's face when she saw he seemed to be having fun with the new boy in their class. It was only inevitable, that when Leo and Luna were older teens, Luna was always going to want to make sure the best things were happening for him, as just at the age of 6 years old, she was checking to make sure that he was having fun; it was clear to her that he was enjoying himself when he had a smile plastered across his face, as the tower he was building with Kyle was becoming more and more complicated. 

Seeing her little brother happy, definitely made her happy.

Meanwhile, back at the Mafia headquarters... "Do you need help with any of this?" Chara wondered, as she had perched herself on the edge of Frisk's desk. The other human girl seemed like she was shifting through papers about a bunch of mumbo jumbo Chara didn't even get. The fact that Frisk even seemed like she knew what she was doing was baffling to Chara, because sometimes it was easy to forget that this was the same girl she had met when Frisk was only 19 years old, and back then she had been so different. 

Now, she definitely was a lot more sophisticated, but Chara didn't know if this was the right path for her, even if she was helping people keep their jobs. She imagined Frisk being more involved with her family, and she knew that if Frisk chose to do this, she would be more involved with her job than them. "No, it's okay. Thanks for offering though." Frisk had smiled kindly towards Chara, before facing her two eyes back down towards her desk. Chara frowned. 

"...Are you sure about this?" Chara spoke up, only to get a bewildered look from Frisk, as if she didn't know what she was talking about. She exhaled. "Asgore quit this job because it was so time consuming. Because Toriel was so sick of him getting caught up in work." She explained. "I just don't want to see you and Sans fall apart after all the work you guys have put into your relationship. Especially when you're supposed to be getting married." Surely, Frisk shouldn't find it completely crazy that she was concerned; she wasn't the only one who was. Despite everyone's concerns, Frisk felt like she could handle what she had brought onto herself.

"I'll be smart about it. Really." Frisk told Chara with a warm smile. "I haven't forgotten about Sans, or the kids. They actually have their play they're doing in kindergarten soon. I can't wait to see it." She said, seeming genuinely enthusiastic to watch Leo and Luna's play. That at least made Chara feel a little more relaxed, that even though Frisk knew she had a busy job, she was still seeming to think about her family. She just hoped things stayed that way, because Chara was extremely happy for Frisk, and that skeleton. They were meant for each other, and the last thing she wanted was to try and go running around again trying to fix things between them. She had already been their cupid once, did she really need to go and do that again?

True, it's not like she had to do that for them. But she cared a lot about the happiness of her sister, and the last thing anyone wanted was for that skeleton to become all grumpy and miserable again if him and Frisk split. Chances are, he would act one way in front of the kids, seeing as he wouldn't want them to see him unhappy, and then he would act another way in front of everyone else; he wouldn't care about having to hide how he felt around grown adults, right? That was just her guessing what it would be like though. She didn't know. 

All she could hope was that Frisk would be smart about this.