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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It was Christmas Eve! How exciting. 

How crazy that it was already here - Christmas Eve. It really felt like the past month had completely flown by, and the end of this year really had a range of different things going on, (with some of those things being pretty emotional). But because the end of this year had been pretty hectic, Sans and Frisk were a little behind on the decorating. Not that that really mattered, because at the mention of decorating the house in tinsel, and actually putting up the Christmas tree at last minute, the twins were ecstatic for such an idea. It at least gave them something to do for the day, and it would likely make them feel all the more Christmas-y in the long run. 

"Can we put a pwetty angel on top of the tree?" Luna was asking excitedly, holding up the exact ornament within her hands, as the skeleton was busy putting the tree up. Frisk smiled at her happy, excitable daughter, and was almost ready to reply, at least until Leo butt in, holding up what appeared to be a star.

"I want a star though!"  

"But we had a star last year!" Luna argued back, slightly pouting at her twin brother, who could only look back at her in disappointment. "Pwease can we have a pwetty angel?" Luna pleaded, while Frisk lightly giggled at the two kids trying to bicker back and forth about whether they should have a star or an angel on top of the tree. It wasn't like they were even angrily arguing with each other, but they were just trying to convince the other sibling of which they should choose. To be fair, they were normally supposed to take turns, so...

"Leo, we're going to have an angel this year, okay?" Frisk told the boy softly, who immediately looked disheartened by the fact that he didn't get to put the star on top of the tree when they would be finished with decorating. "You did get to choose the star last year, and you know we always take turns, which means you'll get to put the star on next year, okay?" Frisk continued, while Leo sighed and sadly nodded. It made Frisk feel a little guilty seeing him made a little upset by their conversation, but she had to be fair. 

"the tree is up." Sans spoke up, causing the three chatterboxes to glance towards the now standing tree with bright smiles - even Leo was smiling a little more now that he saw the bare tree standing. Now, they would be able to decorate the tree, using decorations that they had in a box, that was placed to the side, near the tree. Seeing that the tree was up, it was no surprise that the twins darted towards the box to start picking things out. Frisk giggled once more, hearing Sans lightly telling them to be careful, just as she heard a knock on the door.

"I'll get it!" Frisk said, as Sans was lifting Luna up to let her put a Christmas ball-ball in the middle of the tree, while Leo was working on hanging some small ornaments at the bottom of the tree. Going to reach for the handle, Frisk swung open the front door, only to smile widely when she saw who it was. "Kai! Hey!" Frisk said, as her and her friend shared a friendly hug. It was actually a couple of days ago that Frisk had called Kai up, to see if it was possible for Kai to put in a good word for her and get her her job back. She had yet to hear back about whether her old bosses were going to rehire her, but she had her hopes high, after all, Mina and Kaz were fairly friendly and understanding. For bosses, you would expect them to be much stricter, but funnily enough, they weren't.

"Hey, Frisk!" Kai beamed. once they pulled away from the hug. She lifted a small plastic bag within her hand, which looked like it had a couple of items within it. "I bought you guys some presents. There's one for you, Sans, Leo and Luna. Seeing as I can't pay you guys a visit tomorrow for Christmas I thought I would do it today." Kai told her as Frisk allowed her inside, considering it was fairly cold outside, seeing as it had been snowing again the night before. 

"That's so sweet, you didn't have to do that!" Frisk said, smiling down into the bag that Kai had just handed her, with a few presents clearly wrapped up within the bag. It was really amazing how giving people could be at this time of the year, because it was actually earlier this same day that the mother of Leo's friend - Kyle - came by to drop by a gift for Leo, saying it was picked out by Kyle. How kind that even small children could even be so giving at a time like this. 

"You haven't even decorated your tree yet?" Kai asked in surprise, when she was allowed into the living room, to find Sans, Leo and Luna all decorating the tree together. Leo had been adding lines of tinsel around the bottom, while Luna had been hanging various decorations in different places. Sans was working more on the top of the tree, and would sometimes allow one of the twins to help, by lifting them up to help them reach. Frisk shook her head.

"Things have been a little busy, so we haven't really had the chance." Frisk stated. After all, there was her and Sans being apart, and there was her trying to run the Mafia for a short while - which she couldn't exactly tell Kai about. Though, of course the green haired girl had been extremely happy for her friend when she heard the news that her and Sans got back together. After all, best friends always wanted the best for each other, and it was clear in the time that Frisk and him had been apart, that she had been pretty unhappy. Kai wasn't sure she had ever seen Frisk so tired that day she had said she wanted to quit her job. But now, she looked a lot better once again. Like her usual self. 

"Oh, right." Kai laughed. 

"Do you like it so far, mommy?" Leo wondered towards Frisk and Kai, causing Frisk to nod. Most people might not have allowed their children to help decorate the tree, because it would end up looking pretty messy - after all, they were only kids who were just doing something for fun, and weren't really thinking about it in a strategic kind of way. But Frisk couldn't really care about having a "flawless" tree. What was more important to her was knowing they all decorated it as a family when she looked at it, and that was enough to warm her heart. Even Kai who was standing next to Frisk gave the 6 year old a thumbs up to say that she liked it. 

"What are you doing for Christmas, Kai?" Frisk wondered towards her friend, who rose her eyebrows a little in thought, as she looked up towards the ceiling.

"Well... Me and my mom were planning to go out of town. They're doing this thing where they're switching on all the Christmas lights, and my mom really wanted me to go with her to see it, so that's why I won't be able to visit tomorrow." Kai pointed out, while Frisk nodded, commenting how that sounded like a lot of fun. Her, Sans and the kids were just staying inside in the warm for Christmas this year. Maybe they would go out and play in the snow for a bit, before eating Christmas lunch, but apart from that, they could all just open presents inside, with the house being all nice and toasty. They could all wrap up together in cosy blankets, sitting on the couch to watch Christmas movies. Luna's favourite Christmas movie was How The Grinch Stole Christmas - the one with Jim Carrey in it. So, they tended to watch that every year.

"Would you like to help us decorate the tree?" Frisk wondered towards Kai, who looked surprised at the invitation. "Unless you have to be somewhere?" 

"Yeah, I only came by to drop the gifts, and for a short chat. I have to visit my grandparents too, so..." Kai explained. 

"it was cool seein' ya." Sans decided to finally speak up from where he was standing, as he had been more busy focusing on what they were doing with the tree, over talking to the visitor that they had within their house. The green haired girl beamed kindly towards the skeleton, saying the same in return. After all, she considered both Frisk and Sans as her friends. It was nice to not be intimidated by the monster anymore, and to actually be able to consider him as a friend. 

"See you Kyeee!" Luna called happily, waving to Kai as she was leaving. Kai of course happily waved back, before she was gone from sight. 

"Alright, let's get the rest of this Christmas tree decorated." Frisk said, as she went to join her two kids and her fiance in decorating the tree. Sans grinned towards her, clearly seeming just as joyful as her that they were spending this time together; this day together. The worst thing that could have happened could have been them spending their Christmas' separately. But no, they were spending it here, together.

As a family.