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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She had thought that maybe she would end up seeing her little brother later, that perhaps their daddy would drop him off into kindergarten later in the day; that isn't what happened. Instead, Luna didn't end up seeing Leo for the rest of the day at kindergarten, not even when her mother - Frisk - was waiting outside to pick her up. To tell the truth, the 6 year old would be lying if she had said she hadn't been mentally wishing that she would see both her parents, with Leo waiting for her. Because she knew that if her mom and dad were together, then that meant that they weren't still angry at each other, and they weren't fighting anymore, right?

But he was nowhere to be seen. So dad, no brother, and it did sour the little girl's mood a tiny bit. She wanted them to be a big happy family! They would be that again, wouldn't they? She really hoped so; she did not want to think that maybe she wouldn't get to see her daddy as much anymore, or her little brother. She didn't like the thought of being separated from them all the time. Already, she was missing them quite a lot, and she wished they were here. 

"Hey, Luna. Did you have a good day?" Frisk wondered with a smile, of course keeping positive for the small child who would likely immediately be able to tell something was up if she clearly did not look happy. It was like what Sans was trying to do with Leo: keep on a happy-go-lucky facade for the sake of the child's happiness, because it wasn't like she was happy, and it wasn't like the skeleton was happy either. Instead of being happy, Frisk actually felt super tired, not just from work but this whole situation. She wanted to fix it, but for once, she wasn't quite sure what to do about it. 

"It was okay... I miss Leo, and daddy..." Luna admitted sadly. "We will see them again, won't we?" Her saying that, made it sound like the two of them had completely vanished forever, like they were just gone from existence. But with a child's over imaginative mind, she was probably thinking that they were just gone, and that maybe they weren't coming back. To tell the complete and honest truth, Frisk didn't really know what was going to happen. She didn't know whether Sans would come back with Leo and hand him over to her and decide that was for the best, or if he would come back and they would talk things out... She wanted to talk things out, but she found herself feeling afraid and worried. 

Frisk didn't want to lose Sans forever, she knew that. She loved him; adored him with all of her heart and soul, and she knew she wouldn't trade the day she had met him for anything else. In fact, she could do it a million times over, starting from the very day they met, reliving all that they had gone through over and over, because it was all such a huge part of her life that meant everything to her. Before that day of running into the skeleton and that tall goat monster, she thought that she would be left for dead, and that she would only starve on the streets. Ever since her parents had died, she had felt like her life was done for, and part of her had questioned why she even tried to continue to survive, when she had no home to go to. 

Luckily, she tried her best to stay positive, and Sans gave her a home. He gave her all she could possibly want. Love, a family, he was going to give the rest of his life to her, by marrying her; his love ran that deep for her. She knew he cared. She knew he only wanted what was best for her, what was best for them. However, as much as she wished she could simply back out of the decision she made, she felt like she would feel too much guilt to just drop people like that, who were relying on her now to keep them employed. 

Not only was she thinking for people who she hadn't even had that much interaction with, but she thought about Chara, and Asriel, and Blair, and Andrew... Her friends. The last thing she had wanted was to let them lose their jobs, especially with how hysterical Chara appeared when her father said that he was stepping down. She had to do something, and while part of her regretted her decision, what would have happened to everyone else if she hadn't done something?

"Don't worry, Luna... They'll be around, I promise." Frisk didn't know what else to say, other than that, because she didn't know what Sans would do. She didn't even know what he was currently up to as they spoke. Chances were, Sans was probably at his father's, spending time with Leo, or something like that. 

"I hope so..." 

From  then on, the parent held the child's hand, as they walked home in complete silence, likely having a lot of things on their mind. Even now, Frisk tried her best to keep smiling; that didn't mean she wasn't thinking a lot, about Sans and Leo. Funny, Sans was normally the one who liked to worry about and overthink everything, but here she was, constantly worrying. In other situations, it had been easier to just switch off, be positive. However, the fear of losing the one she loved, and possibly ruining the lives of her children was just too great for her to feel like she could mentally relax. None of this was just about her, it bothered Leo and Luna too, clearly.

What could she say to Sans, so that he knew she was sorry? Was it still too soon for them to talk things out in a calm, collective manor? Probably. While she wanted to fix everything, the last thing she wanted was to be pushy, causing Sans to snarl at her in frustration and impatience at her attitude. She really hadn't been smart, had she? "Hey, Frisk!" 

"Huh?" Stopping in her tracks upon the sidewalk, while they were literally just down the road from their house, Frisk turned around, only to see that familiar face from her work - the girl with the freckles, and the green hair. It was Kai, from her other job. Her job that she hadn't actually been attending that much lately... Letting out a small nervous laugh, Frisk beamed towards the girl who was seeming to catch her breath after probably running after her. "H-Hey, Kai. You look like you ran a marathon."

"Well, I wanted to talk to you, because I saw you walking. I was yelling after you at least a couple of times, but it's like you were a million miles away." Kai breathlessly laughed. "It's been awhile. How come you haven't been in work lately? Mina and Kaz--", (their bosses) "--have been worried about you... I've been scared that they've been thinking of letting you go." She mentioned while nervously wringing her hands within one another, as if to enhance her own clear fretting. Kai didn't want Frisk to end up losing her job at the cafe, only because Frisk was her friend, and felt like a best friend at that, ever since they had been working together. It felt nice, to have another helping hand deal with the customers, but when you were on your own, with no one else to help you, it started to become stressful.

"O-Oh, I, um..." Frisk glanced towards her daughter Luna, who was gazing back and forth between the two adults. No way, could she give Kai a truthful answer as not only was her job a secret from any outsiders, for a clear and obvious reason; her and Sans had promised to each other that they would never talk about the Mafia in front of either of the children. They would never find out about it, for as long as they lived. True, it would probably be more difficult to keep it hidden from them when they were to become teenagers, but she wanted to keep them innocent for as long as she possibly could, and she knew that Sans had agreed with her.

"You even look super tired... Have you even been sleeping?" Kai pointed out, not finding it that difficult to notice the fact that Frisk was beginning to form dark circles under her eyes. Glancing elsewhere, Frisk wasn't really sure what to tell her. Maybe she hadn't really slept well since falling out with Sans, but again, she didn't want to talk about that subject in front of Luna. Luna was already worried that their family was crumbling to pieces, and she didn't want to make the 6 year old feel worse about it.

"Kai, I'm fine." Frisk reassured her, smiling her brightest smile. "Though, I don't know if I'll be coming back into work..." Back when she wasn't so involved with the Mafia, carrying two jobs felt like it would be pretty easy - and it had been. She enjoyed having two jobs at once, because in one place, she had all her old familiar friends - her family. And then at the cafe, the atmosphere there was really nice, and Kai was of course her friend. Sadly, she wouldn't be able to maintain the time for both. 

"W-Wait, what?" Kai questioned. "You mean, you're quitting?" Kai asked sadly, and Frisk could only give a small nod, definitely feeling guilty when she saw the disappointed expression plastered across the green haired girl's face. She was quiet for a few seconds, until exhaling and beginning to nod herself. "O-Okay... I'll let Mina and Kaz know if you want." Kai offered, trying to be helpful. 

"That would be great, thank you..." Frisk said. "Anyway, I better go, Luna here has had a long day." Frisk lightly giggled towards Luna, who flashed a small smile at the mention of her name. That being said, Frisk and the 6 year old girl went to continue on their walk to their destination - their home - while leaving Kai feeling glum upon the sidewalk. Frisk wanted to say she was sorry, but there wasn't much else to say. She just wouldn't have time for everything.

And she knew that was her own fault.