Sans POV

"Yeah. Let's do it." She looked pretty damn determined. I grinned. "then le's get started. It was all falling into place. As long as she held that brat in as long as she could, it gave me time to get started on the real project. The machine in my basement. I'd been building it to trap the Player, though due to the resets, I never got to finish it. She was giving me the time I needed. While she slept, I'd go there and work on it while the Player thought this thing here would be the trap. It seemed fool proof. I just hoped it worked. I took out the paneling to shut down the extractor. Don't need her getting her determination extracted on accident. I looked at her while she waited for something to do. My soul pulsed with the desire to mark her as mine. I almost told her how I felt. The day they killed Papyrus, just an hour before.. but I got cold paws. How could someone like her ever love a beast like me? What we had now was good enough. It was miracle enough that my soul mate replaced that little brat in the first place. "hand me tha' screw driv'r there."
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She went to sleep and I went to my lab. "now th' real work begins." I pulled the tarp off and started fixing up and replacing rusted parts. The wiring looked great. Nice an clean. No mice got to it or nothin'. It was mainly the outside parts that needed replacing. Of course, it still wasn't done. There was still quite a few components that needed to be added. That's why I had her holding the Player back. There was no way I could get this done before she got to Judgement Hall. After all this shit was done, maybe I could even work up the courage to ask her on a real date. "in yer dreams, sans. she's to perfect fer ya." But a guy could dream. Boy did he dream. He dreamed of living on the surface with her, her loving him as much as he loved her. He dreamed of starting a family with her and raising their children. They'd be so perfect, feral yet tame. A little girl maybe. She'd be as beautiful as her mother. Or maybe a boy. He could be a handsome little devil. Sans would be a good father, who didn't harm his pups and no doubt [Y/N] would be the absolute best mother. He smiled as he worked. They were merely dreams though.
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"Sans.." [Y/N] looked to me. I could feel it. The Player wanted control. As far as they knew, this machine was their doom. They probably wanted to destroy it. Make sure I could do nothing. "hurts?" It was more a comment then a question. She nodded. "c'mere." I hugged her close, reassuring her that this was the right thing. "just hafta hang on fer a little bit longer. it'll be ok, sweets." Having her here, holding her close like this. It felt so right.. she nuzzled into my jacket, to bad she was asleep now. If she'd done that while she was conscious, I would have probably claimed her then and there. "good night, [Y/N].. love ya.." I was tempted to doze with her, but I didn't have the time for that luxury. It was time to get back to work once more. I laid her on the gurney she'd been sleeping g and teleported to the basement. "i won' let ya suffer forever. i'll help ya, sweets."
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It's been a few days now. My soul mate was having a wild time with the brat. If they didn't stop fighting, I'd give them a wild time. I growled as another wave of fear, pain, and determination surged through my soul. What a fuckin monster. She wasn't wavering in the slightest. What was giving her the drive to stay this determined anyway? Was it the machine? Or something more?
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Your POV

LET ME OUT! THIS SHOULDN'T BE POSSIBLE. "Well y-you know me.." You hissed. "I'm a w-woman of impossibilities.." They really wanted to destroy Sans machine. You couldn't allow that. Sans and his machine were the only things keeping your determination going. You couldn't understand why Sans told you his plan though.. the Player heard everything which is why you were having this problem. They wanted to destroy the machine then take Hotland. "kid.."
"Sans..?" He smiled sadly. "i don't wantcha hurtin'." You sat up from your spot on the gurney. "Sans.. w-what are you saying..?" He avoided eye contact. I sealed the machine so the Player can't get to it, but.. ya should let 'em go. ya won't hurt no more, i can finish it while they attempt to get at it. nobody should get hurt." His tail tucked, like he was ashamed of making the suggestion. It hurts, but the other monsters were your main concern... Sans especially. But he'd been right for the most part. What is he planning? Is he serious?

Let them out?

Stay determined?