Author Note: So, there's some mild NSFW in there, but nothing that is really all that of a big deal. Whether there will be another moment like this further on in the story, but it's not interrupted (( ͡° ͜ʖ ͡°)) I don't know. Depends how people react to this I guess. 

Anyway, enjoy and don't go complaining. Because I did warn you! 

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Arriving back home, Sans exhaled after calling out Frisk's name to see if she was home, only to get no response. Clearly she was still out with Ajax. 

Closing the front door behind him, he went to shove his hand into his coat pocket, taking out the small box which sat inside, and he opened it up to reveal the beautiful diamond ring staring back at him. He really hoped she would like it. And that he'd even be able to build up the courage to ask her properly, he didn't want to mess this up. 

Hearing a key in the front door, startled, Sans quickly put the box back into his pocket, just in time for Frisk to enter with a frown set upon her face, until she saw that Sans was home and her dull expression lit up instantly, as she was clearly glad to see him. 

"heya, kiddo." Sans grinned at her as she walked over and gave him a hug. "ya alright?"

"Yeah, you?" She asked with a sigh. "I'm just tired, that's all. Did you have a good day? I hope I didn't make you feel bone-ly." Frisk murmured, causing Sans to chuckle and shake his head. He pulled away from the hug and looked at her, staring into those two bright green glowing eyes of hers. They were so elegant, so deep that he felt like he could get lost in them every time he just stared and stared. To think that this was the girl that could be his future wife, he felt so unbelievably lucky. "Sans?" Frisk questioned, raising an eyebrow as he still hadn't answered her. Realising that he had completely spaced out, he rose his own eyebrows and lightly blushed. He hadn't meant to get lost in his thoughts like that. See, he could just get lost in her eyes sometimes.

"heh, sorry. i was just gonna say that it's been alright, ya don't have to worry 'bout me." He told her. "though, are you sure you're okay? you didn't look too happy when you came through the door."

"Yeah, yeah I'm fine." She replied, just shaking her head as she seemed like there was something she didn't want to talk about. Sans wasn't sure whether or not to push it, or whether he should just leave it. 

"did ajax do something?" 

"You could say that." Frisk said. "Well, he said something that was just irritating and... Look, Sans, it's about work. And I already told you I couldn't really tell you anything about it... You'll probably find out soon enough anyway." 

"what's that supposed to mean?" 

But instead of answering him, Frisk just told him to leave it as she went to go to bed. Furrowing his brow, he stared after her but decided not to add anything else on the subject. Clearly she was tired and fed up about whatever Ajax had said, and Sans didn't want to put anything else atop that stress. So, instead he asked if she was hungry and if she wanted something to eat. When she told him she was fine and that she just wanted to sleep, he silently nodded and left her to her own thing.

It did get boring though, just laying around on the couch, just trying to find something interesting to watch on TV for the past several hours. He wondered what got Frisk in such a bad mood, what had Ajax done or said that made her feel miserable? The skeleton must've really had a foul expression upon his face because when someone entered the room, they spoke "If you keep your face like that, it might get stuck." which brought his awareness back to the real world, rather than on the inside of his head where thoughts tended to wander. Frisk had woken up, and she was just standing with a blanket wrapped around herself as she looked over towards Sans. 

"heya kid. wanna sit down next to me?" He wondered, patting the couch beside him. She quietly nodded and walked around to join him. With a faint smile, Sans placed his arm across her shoulders and pulled her close. "so, what did your 'friend' do? did he really irritate you that much?" He chuckled with a grin. 

"A little bit." She admitted. "It's just, I thought he just wanted to hang out. Try not to think about work and maybe move past our differences, the way we view monsters in different ways... His view of you guys... Isn't exactly the best." 

"so you've mentioned." Sans simply replied with the shrug of the shoulders. "so, what's the problem?"

"He turned the whole day into a work thing. Just talking about work nonstop. About how he's been chatting with some of the higher ups to get him up there with them. So he can start deciding rules, the way things go." She saw the worried look on Sans' face and put a hand on his cheekbone, beaming sadly at him. "Hey, it's okay. You don't need to look so anxious. He probably won't even be able to move up in the ranks anyway. He just thinks he'll be able to. There's still a whole process he's got to go through before he even makes it to the top." 

"still... i don't like the idea of that chump decidin' how things go." Sans murmured with a frown, Frisk nodded, completely agreeing with his comment. 

"Yeah, you're right... I don't either." She exhaled as she took her arms and hung them over Sans' shoulders. "But it'll be fine.... Can I ask you something, Sans?" 

"of course. shoot." He spoke, allowing for her to say whatever was on her mind. After all, even if he was a bit of a hypocrite - seeing as he didn't always talk about everything, he didn't want her to bottle things up inside. That didn't mean he would try to force things out of her. If she didn't want to speak, then she didn't have to. But if she willingly wanted to get something out there, something that was on her mind, something that she just had to say, then he allowed her to do so.

"...You'll always stay with me, right? No matter what?" Frisk quietly wondered, which caused a look of bewilderment to spread across Sans' face. Though, it disappeared as quick as it appeared. If only she knew. If only she knew that she was the exact person that Sans was planning to spend the rest of his life with. 

"frisk..." Sans sighed, taking one of his hands and placing it under her chin, to lift her eyes back to his. "you know that i'll always be with you. no matter what. and i mean that." He told her in a calm, loving tone whilst he slowly pulled her in for a kiss. Frisk's cheeks blushed a light shade of pink, as her eyelids fluttered closed and she melted into his close embrace. What had she done to be so lucky as to have someone like him? What had he done to be so lucky as to deserve someone like her? These were thoughts that were running through both their minds in this gradual, affectionate moment. 

When needed, the two took their faces apart for air, and their eyes locked again while small giggles escaped from the both of them. Sans placed his arms lightly around her back, and she kept her arms around the back of his spine. Again, they leaned towards each other, mouths meeting and tongues dancing elegantly in sync. Frisk had been very surprised the first time she had made out with Sans to find he had a tongue, but magic worked in mysterious ways she guessed. 

"Well, I'm glad." Frisk finally spoke again, when she removed her lips from his mouth once more. "Because I never want to leave you. And I never want you to leave me - not that I believe you'd do something like that. I'm just worried I'd do something stupid like... I don't know, causing the timeline to reset again, and then you'd hate me forever." She said. 

"i know you ain't gonna reset again, frisk... i... i believe you. i believe you now, when you say you won't..." He responded, pulling his face into a frown. "at first, i have to admit, i had my doubts. i even had to talk to gaster about how i felt, about my worries..." He admitted, looking away when he saw the expression of surprise upon her face. "but he just told me not to worry. to believe that you won't reset again. and it wasn't that i thought you'd do it just for the hell of it. i've just been scared that something would happen to cause you to reset, or i'll do something stupid and make you hate me." He sighed. 

"I could never hate you... Ever. Even after everything we've been through, all the timelines... The fighting, the resets, dealing with Chara... Everything. I never want to turn my back on you." She whispered, placing her hand on his chest to push him down onto the couch as she stared down at him with a tender look in her eyes. "Because I love you." 

"i love you too, frisk." He replied in a calm, loving tone before they shared another kiss. Sans knew his cheekbones were likely beginning to be mantled with cyan blush as he kept his arms around her and his eyes closed, just sinking into the moment, just enjoying every single second of being here with her. Once more, the couple broke into hushed caring giggles as their eyes just stared over the other person's facial features. To Sans, Frisk was like an amazing, beautiful princess, or like a goddess from another world. And for some reason she had decided to settle for someone like him, and sometimes with the way he was, he couldn't help but question why.

"honestly... what made you fall in love with someone like me?" He quietly chuckled. Frisk smiled at him in return, once again going to put her hand on his cheekbone, giving him a small kiss before replying. 

"Because... You've always been someone who I felt like I could talk to. Since we became friends, I've always felt like I can trust you with things I tell you, and you've always been there for me. Even when I've gone on the wrong path, you were there to point me in the right direction. You didn't give up on me. You stayed by my side through everything, even when I felt like I didn't deserve it... And you're one handsome skeleton." She teased. 

"well... i'm your handsome skeleton." He answered cutely, causing her to move her lips back to his mouth, which he was more than content with as he felt her hands move to his hoodie. He couldn't help but blush profusely, knowing that she wanted him to remove it - not that he wanted to argue against that as he sat up a little, going to help her with that task of removing it from over his plain white shirt. Once removed, Sans just lazily tossed it to the side, not taking his eyes away from Frisk's for even a second. 

Laying back down, the skeleton softly groaned, feeling Frisk's lips beginning to nibble at his spine. He could tell she liked the response, because he could see the smile on her face when she had moved to give him yet another kiss, which he gladly returned with affection. This girl, she was so perfect, so stunning, so... Just amazing. And he cared about her a great deal. He cared about her more than words could really describe. She was his everything, his world. Which is why he wanted nothing more than to make that one night untarnished, where he would ask her to marry him. It was going to be the next biggest step of their lives, and he didn't want to mess it up.

Still, Sans couldn't help but blush from embarrassment as Frisk managed to get these small sounds out of him, simply from continuing to kiss and nibble at his spine. Honestly, he never expected such a reaction, yet here he was just allowing for Frisk to do her thing as he was already beginning to make noise. And it didn't help when she was teasingly going lower, ending up at his collar bone and kissing at it. But clearly she was loving every second of it with her lips pulled into a sweet smile, and he didn't exactly have the intentions to stop her either. 

With all the touchy feel-y going on between the two, just showing their love towards one another as they continued to shower each other with kisses, they hadn't noticed that the front door had in fact been unlocked with a key, meaning someone was on their way inside. And boy, both Frisk and Sans felt like they wanted to absolutely dig themselves a hole and die when Undyne was standing in the doorway, clearing her throat. They hadn't even been aware of her existence until she had to go and make a noise. 

Luckily for both of them, no one was exposed. Just the simple hoodie tossed to the floor and the fact that Frisk was laying on top of him was the only evidence that they were clearly up to something. 

"U-Undyne!" Frisk yelped, quickly climbing off of the skeleton who then sat up, blushing the darkest shade of blue Undyne had ever seen as he glanced away nervously. "W-We... Uh... Didn't know you'd be home yet!" 

"You do realise I've been sleeping there, right?" Undyne commented which only caused them to be even more embarrassed. "The last thing I want is to sleep in the place where you've gone and done the do." She laughed, seeing how flustered they were as Frisk was trying to stutter out an explanation. "Don't worry you two, it's fine. I get it."

"I-It's still e-embarrassing!" Frisk stuttered. She sighed and looked over to Sans who glanced her way and gave her a small smile. 

"Well, hey, if I'm interrupting something so important, then go get a room." Undyne joked. This was what really caused both Frisk and Sans, who quickly grabbed his hoodie, to bolt out of the room from pure awkwardness as Undyne had pretty much caught them at the act.

"Uh... S-Sorry about that..." Frisk murmured when they were once again alone. "Uh... I don't really think I'm in the mood anymore." 

"heh... yeah, me neither." Sans answered, scratching the back of his skull, still blushing all the while. "maybe we should, uh, go to sleep for now?" 

"Yeah, I agree." Frisk smiled with a nod. "Uh... Sans, I just want to say... Thanks for... Making me feel better." She spoke, causing him to raise his eyebrows at her. "I was feeling pretty miserable after spending the day with Ajax. And honestly, I had really missed not seeing you all day... So, thanks." She finished, filling the room with momentary silence until Sans chuckled and grinned at her in return.

"it's fine, kid. you know i'll always be here for you. no matter what." He said.

And that was the truth.