Sans' body shook as he stared down at the dead human with blank sockets. Though he had no lungs, his chest moved rapidly as cold puffs of air floated from his clenched mouth. His bloody hand quickly dropped the even more bloody thighbone he had used as a weapon and took a few rapid steps backwards. He... he didn't mean to! It was only supposed to be a mercy killing, like all the others. He knew that, if this human made it past him, Undyne... god, who knew what she'd do to the kid. Probably worse than what he himself just did; not that it excused his actions.
Taking another step backwards, the skeleton glanced around the area. No one was around. Good. Turning his gaze back towards the dead kid, Sans watched sorrowfully as a green soul floated from the body before disappearing into the trees. Damn, even after having several of their limbs cut off, the kid had struggled to live. It ached at Sans' own soul as he slowly approached the nearly unrecognizable human and re-picked up his weapon.
He couldn't leave the human out in the open like this; monsters would smell the blood and come looking. He couldn't just bury it either. The body was too badly damaged; the snow and dirt would surly rot it if a monster didn't find it first. So, finding no other choice, Sans slowly knelt next to the human. A few blue tears managed to to slip from his sockets and rolled down his cheek as he raised his weapon, smiling pitifully at the dead child.
"Heh, sorry kid, nothing personal. Just close your eyes and it will be over before you know it." And, without hesitation, he brought down his weapon.
I struggled a little with what to have Sans say. If you have a better idea let me know and I may edit. Oh and I am taking on more of a Sour Apple version of Horrortale, since I don't know the other one.
Anyways I got a new laptop so I can start writing again ^^. Hope you like this