An Oath of Mercy || UnderFell Sans x Reader

prologue

Everything was perfect. It was late summer, the ideal blend of warmth from the setting sun and cool from the light breeze to achieve the perfect temperature. You were on top of a mountain with the love of your life, Leon, and the two of you were basking in the sun's last rays as you walked hand in hand. In his other hand was a picnic basket containing yummy treats you planned on feasting on once you reached the clearing up ahead. It was your 2 year anniversary and he insisted on climbing Mount Ebott to enjoy the beautiful sunset and a hand-crafted picnic meal.

You spread out the blanket on the green grass, smoothing your red skirt down as you sat and wrapped your white lab coat around yourself. You insisted on wearing it—Leon had picked you up from your internship (clinicals) at the local hospital, and they had finally given you your own doctor's lab coat. To say you were excited was an understatement.

"...and since I told him it was our 2 year, he let me go a little early," you were explaining to Leon. He was nodding as he set out the to-go containers of lasagna on the picnic blanket, then froze.

"Wait, you're wearing a white coat." Panic flashed through his eyes as you laughed, taking his hands gently.

"I don't mind. I can always just clean it before tomorrow." At your reassurance, he calmed and continued placing out the utensils. You reached to help him but he snagged the basket away. "Um, don't worry, babe. I got it." You rose a brow at his odd behavior but conceded. You turned your gaze skyward with a content sigh.

"You were right...this view is amazing." The sunset lit up the sky with waves of pink and purple, and down where the sun was slipping below the horizon, a concoction of reds and oranges. It was breathtaking.

"Well it's our anniversary, so..." He swallowed, his hands shaking the smallest bit. It was clear something was bothering him.

"Hey, I know it's been kind of rocky lately with all my schoolwork and working at the hospital and everything..." You send him a saddened look as you play with your hands. Sure you two hadn't been on the best terms lately—it was no wonder he was nervous—but he knew you didn't mean to be short with him. You were stressed! You were on the pre-med track so it really wasn't that surprising, he knew that when he asked you out. But since he still wanted to celebrate today with you, you had to assume he didn't hold it against you. "But thanks for this. I think we both needed it." You smiled with your eyes closed, missing the way he nodded nervously.

"Yeah, of course."

At the sudden temperature drop, you realized the sun was almost gone. You stood quickly to try to follow it, wanting to see it just one more time before it disappeared and you had to go back to your stressful life. It felt like a momentary escape, as silly as that sounded. You sighed, shuffling backwards as the sun officially said goodbye until tomorrow. You were kind of hungry, and no doubt Leon was wondering why you ran off. Perhaps you were a little too sentimental, no?

Suddenly, you felt a root snag your foot and you fell backwards. You expected to hit the ground instantly, laughing about your clumsiness as Leon fretted over your bonked noggin. But you just kept falling. And falling. You watched the hole above you grow smaller and smaller until you landed on your right leg, a clean snap ringing throughout the cavern you landed in.

You screamed. You swore you were seeing stars as you reached for your broken leg, unsure for a long moment if you should try to get off of it or if that would only make it worse. "Help!" Leon had to hear you, he was right next to you- but you had run off. Maybe he couldn't. That thought brought a fresh way of panic. "Leon!!" No response. "Leon, please! Help me!" You couldn't help the tears streaming down your cheeks—all you could feel was pain, and you could see the blood seeping through your clothes and becoming a puddle around you.

Everything was perfect. But now you were hundreds of meters down in a hole without a way out.