Part of him thinks that you look better like this. There's a beauty in damaged things, he's come to realize, and the human body is no exception. Cut it and out floods a stream of brilliant reds. Break it and it blushes in tinges of purple and blue. Maybe this is why Sans has come to like the look of you sprawled beneath him, bruises spreading like watercolors over the canvas of your skin and your limbs heavy with the weight of defeat.
Yet there's a hesitancy in his satisfaction. He can still recall the warmth of your skin pressed against him, your voice quiet and soft in the velvety dark. The caress of your palm along the length of his spine. It's images like these that haunt him in this timeline: little mementos of a disappeared past, intersecting and intermingling with the present, that direct his attention to the gentle slope of your neck as he snaps it, to the startling redness of your mouth when you spit out a broken tooth.
And isn't this intimacy, flesh pressed against bone and you sprawled before him, vulnerable and waiting? Your clothing disheveled, a brief glimpse of skin. Sweating, panting, crawling on the ground on all fours. Is this surge of arousal so surprising? It's a pulse of raw sensuality, born of desire and disgust and a strange ache of tenderness.
Here you are, flushed with shame but dripping from the very core of you, half-lidded eyes lowered in submission. You shiver in fearful anticipation when he slides the head of his cock slickly over your folds, just enough to let you feel the girth of him pressed against you. Then he sinks into you inch by inch, parting you like a knife.
Sans presses his teeth to your neck in an imitation of a kiss and lets out a soft and shuddery sigh of pleasure in your ear as he hilts inside of you. There's the clench and flutter of your muscles as your body struggles to accommodate him, so exquisitely tight around his length that he nearly comes right then and there, and then the pained little whimper you give when he starts fucking you slow and hard. And god, somehow it feels so right to be sheathed in you like this, with his ribs pressed hard against your breasts and your heart beating fast against his bones. It's like relief washing over him in waves, lust mixed with self-deception as Sans shuts his eyes and tries not to think about the way it used to be - your fingers laced between his and his name on your lips instead of those awful choked gasps that you let out with every one of his thrusts.
He buries his face into your shoulder and breathes in the scent of you, that vaguely floral smell he's come to associate with ash and butterscotch, dust and burnt typha. The rush of your blood pulses beneath his cheekbone, reminding Sans of human physicality, of the carnality of flesh without magic, and he bites down hard into that unmarked skin, capillaries breaking and hemorrhaging under his teeth. The sudden jerk your body gives beneath him makes his cock ache with need, makes him dig his fingers into your hips as he bucks deeper inside of you.
By now you've gone quiet, your face tilted away from him and eyes shut tight as he uses you, breathing shallow little breaths and clenching your fists against the floor. And he knows that you're trying hard to keep some illusion of control, he's seen you close yourself up like this a thousand times, crumpled on the ground and waiting for death.
"Baby," he murmurs, and grips your chin in his hand, "Look at me."
His voice is so inviting, so strangely incongruous with the whole situation that you do as he says. There's such an overwhelming resignation in your gaze that Sans feels something in him faltering, some well of guilt and self-loathing he'd long ago sealed up bubbling up again within him. For a moment he stills inside you, doubt flaring in his empty chest before the glimmer of your broken knife catches his eye. And that hard knot of bitterness inside of him winds itself tighter and tighter again, choking off love, choking off compassion, choking off all those things that make up a monster's soul.
He wonders briefly if this is what it's like to be human.
Sans hitches your legs across his waist and pulls you close, then slams his pelvis into you so hard that you're sure he's torn something inside. You scream this time, you scream so loudly that your voice echoes down the hall and he has to clap his hand over your mouth to keep you quiet. You're cringing away from him, you're crying again, and it's better this way isn't it? Hasn't he craved something painful and deeply personal like this, intimacy and brutality all at once?
Your cries are muffled against his palm and he moans into your neck as your muscles seize in panic and tighten around him. He presses his body hard against you, the softness of flesh encircling him and drawing him into thoughtless bliss, and the pace of his thrusts begins to quicken as he nears the edge of orgasm. For a few precious seconds his mind goes completely blank, white hot pleasure coursing through him as he comes, spilling his load deep inside of you with a few long and drawn out strokes.
And in the post-coital haze that follows, he collapses against you and tries to catch his breath, savoring the satisfaction of release until he pulls away and catches a glimpse of his come flowing from between your thighs, the blue of his ecto tinged red with blood.
So this is what it's like to break apart a lover, cloying sweetness turning to ashes in one's mouth. And this is what it's like to drown in utter self-contempt, wanting to sink into the earth and disappear.
Your voice is quiet in the silence that follows afterwards. "Was it as good as you thought it'd be?"
Sans looks at the bruises forming on the insides of your legs, at your red-rimmed eyes and wet lashes, and feels his last vestige of decency crumbling inside of him.
"No," he admits, "Not really."
"That's what I'm beginning to realize too," you say, and turn your gaze towards the broken knife. The corner of your mouth twitches upwards in the semblance of a smile, "You know, of all the things I deserve to have done to me, I really don't think this was one of them."
There's not much Sans can say to that.
"You know what comes next," he says and begins reaching for his magic again. There's the familiar pull of energy rushing towards him, bunching up and swirling into form, "I'll make it quick."
"Wait," you flick your eyes back towards him and he hesitates, "Please."
He's long since let go of the pressure on your soul, so you very gingerly raise your arms up and cross them over your eyes, "Let me rest for a little while. Give me - give me twenty minutes. You owe me that much at least." Peeking through the gap of your elbow, you can see the outline of a canine skull forming in front of you, light gathering in its open maw, "Come on Sans, even if I could kill you like this, what the fuck am I going to do? Crawl to Asgore? Maybe roll towards him?"
It's a fair point. The blaster closes its mouth.
"Alright," says Sans, "Twenty minutes."