Sans AU One-Shots

❀Nightmare❀ || saturday. (HS)

Pairing: Demon King! Nightmare Sans x Summoner! Female Reader
Prompt: It's the demons' heat week, and (Y/n) offered to help them out with their urges.
Length: 3.5k words
Background: This was in His Summoner (hence the HS in the title) as part of a spicy week-long bonus thing where each of the guys got a day of the week with Y/n to claim her. The goal of the heat week is procreation (i.e. making babies) and after mating, the heat urges go away. This is the only time Nightmare will let them have Y/n, so they better make it count. | Takes place Saturday (the last day of their heat) - after all of his minions. Gotta save the best for last, no?
Notes: Poor Y/n (or lucky, depending on who you ask). Them being a demon only changes how tall they are (at/over 6'4"), their power (they're much stronger than humans), and how they see Y/n (among other things I explore in my full-length story that aren't relevant for this smut-shot). 

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The end of the heat week was finally here, and (Y/n) was relieved. She'd done it, she made it through despite being fucked 6 ways to Sunday, and pride filled her at the accomplishment. As Nightmare predicted, her week was long and hard, but she could confidently walk up to the Demon King now with a smile. She was still standing. "I told you I could take all of them!" Her smile was pure as Nightmare looked down at her, his hands in his hoodie pockets as he stood in the master bedroom. He'd been busy all week reading her demonic books—which was a much needed distraction from his wandering thoughts of her—and the book in his tentacle snapped shut as he considered her.

"It seems you are correct. I am impressed." His tone was even, and (Y/n)'s eyes lit up at the praise.

"Really?"

"Really." It almost looked like he was smiling for a moment, but that was probably just a trick of the light. His summoner glowed in front of him, then his blue eyelight turned cold. "However, do not think this will become commonplace. Letting my minions have you was rather...irksome to hear." Her face flushed in embarrassment, and at his obvious displeasure, she wondered just what exactly he'd heard, before deciding maybe it was better she didn't know.

"But since I did it, does that mean you can finally, um, show me how it's done?" Her gaze turned hopeful as he rose a silent browbone. "You told me on Sunday I should come see you if I had any strength left so you could..." She trailed off, her face warming as she looked away.

He placed a hand on his jaw in thought. "Did I?" She frowned, slightly worried he'd forgotten and thus wouldn't want to make good on his promise.

"Yeah."

He considered the comment before looking down at her. "Were you hoping I would show you how a King treats his mate?" His tone was mocking, and despite how (Y/n)'s face felt uncomfortably warm, she still nodded hopefully. He chuckled and rolled his eyelight. "You foolishly believed me, then." He rested back on the bed and crossed one leg over the other, pretending to be interested in the book once more.

"Because demons can't lie!" she protested, quickly stepping closer. She was only wearing a loose, practically see-through top and panties, and yet he easily kept his gaze to himself—like she didn't tempt him at all. "Did you not want to?" The words came out quiet, but he didn't even look up.

"I have no insatiable lust for you unlike my minions, summoner." Nightmare turned the page with slow hands. "So if you were hoping I would bend you over the nearest available surface and have my way with you, then you are sorely mistaken." Her gaze fell to the floor, disappointment clawing at her heart. She would never force him to sleep with her, but it hurt that the expectations he'd set at the beginning of the week weren't being carried out now.

"I see," she whispered. "I guess you don't reward obedience, then." She could feel his eyelight on her despite her gaze never rising.

"I do," he replied slowly. "Do you desire to be rewarded, summoner?" Her eyes met his, and she smiled awkwardly.