There just really isn't enough Undertale fanfiction (I need more family interactions between Sans and Frisk, damn it!) so I'm attempting to help fix this very serious problem. Keep in mind I was totally winging this fic, so I'm sorry if it's a little awkwardly written. I plan on this having two chapters, we'll see how it goes though.

Slipping up to the usually noisy house, Frisk was pleased to find that, for once, all was quiet this evening. Poking their head cautiously through the front door and giving an initial sweep of the home they shared with Papyrus and Sans revealed the location of neither skeleton. Reassured that Papyrus was gone and that Sans was either holed up in his room or out with his brother, Frisk made a break for the stairs.

Small feet skillfully skipped up the carpeted steps, avoiding the places that were known to creak under pressure, Frisk's backpack bouncing lightly against their back with each bounding motion. The child winced every time the books in their bag hit their sore back, knowing a bruise was sure to be found under their sweater once they bothered to check in the mirror.

Their room was the second door on the right, directly across from Sans's, from which the low bass of his music could be heard. Frisk scrambled with their doorknob for a moment in panic, not wanting Sans to see them now that they knew he was home and not out with Papyrus.

Once the door was opened and closed as quietly and quickly as possible Frisk let out a sigh, listening to see if Sans had heard them return home, but the music remained constant and the short skeleton's door didn't open. Another sigh and Frisk dumped their backpack on the floor, heading over to the single, tall mirror and staring at their reflection.

Hands rubbed at cheeks reddened from earlier crying and the run home, trying to scrub the blotchy color away with the sleeves of their slightly over sized sweater. Giving up after a moment, Frisk instead pulled up the back of their shirt and sweater, turning and craning their neck to get a look at the large bruise forming on their back. Frowning, Frisk gave the blossom of color an experimental poke, wincing at the dull pain that shot through the hurt skin and muscle.

Angry tears formed in their brown eyes the longer they stood there, staring at the mark on usually unblemished skin. Dropping their clothes back into place in favor of stiffly walking to the bathroom connected to their bedroom, Frisk thought about what to do.

Bullies hadn't been a problem at first. In the year after monsters had rejoined society, relations with the humans on the surface world had be shaky at best. Because humans initially feared the monsters' return, a reluctant and cautious peace had settled between the two races. This was quickly replaced by heated tension however, as not everyone agreed on the monsters' presence in the Overworld. It was around this time that some of the human children at school had taken to bullying Frisk.

Sixth grade started out easy, the other children recognizing Frisk as "the child that brought the monsters back" and either chose to stay away out of fear, or make friends out of interest. Either way Frisk hadn't had many negative interactions with the other children until the bullying developed. It started out as just jeers and words, nothing they couldn't handle- so there was no need to tell anyone, but as of today it seemed Frisk's bullies had gained the courage to get physical.

The ten year old gently washed their face in the sink with cold water as they thought about who to talk to about the kids who'd pushed them over, causing a painful and bruise-inducing collision with a desk corner. Frisk hadn't told the principal or a teacher, too shocked and dumbfounded that their classmates would actually hurt them to think about reporting the incident. But now that they were at home, Frisk wished they'd said something.

A light knock on the bedroom door startled Frisk out of their thoughts.

"Hey kiddo, ya in there?" Sans's deep voice was muffled by the walls separating them but Frisk heard the light concern in his tone, so they dried their face and nervously straightened their clothes in a rush, trotting over to the door- wincing a bit when their lumbar muscles moved too much.

"Yes, coming!" Yanking the door open with probably a little more force than necessary, Frisk put on their most convincing smile and looked up to meet Sans's gaze, the blue lights in his eye-sockets glowed brighter for a second upon meeting Frisk's own brown eyes. They stood in silence a moment too long, Frisk nervously fidgeting as Sans stared with his usual lazy smile, though it was more strained now, Frisk noted.

"Why don't you come downstairs with me, eh?" The monster finally asked, making a beckoning motion with his hand and ambling down the hall without waiting for an answer.

Brows furrowed in slight worry, Frisk paced after the skeleton, following him to the couch and settling themselves down in a mimicry of Sans's position on the opposite end. Silence enveloped the two once again and it made Frisk even more nervous. Sans was never quite this quiet, at least not like he was now, this was a thoughtful and expectant quiet, like he was waiting for something.

Frisk avoided his luminous stare, their fidgeting getting worse until Sans finally let out a heavy sigh, slouching further into the couch.

"So you gonna tell me what's up or nah?" If Sans had eyebrows Frisk was sure they would be raised, his expression was one of obvious concern and barely-contained curiosity. "C'mon kid, what's wrong?" He finished softly, gaze dim. There was something about his words and openly relaxed posture that had Frisk instantly bursting into tears, making the skeleton jump in surprise.

"F-Frisk? Hey kiddo what-" Frisk cut him off, launching across the short distance between them and tackling Sans in a hug, completely disregarding their sore back. Sans let them curl into a ball on his chest, Frisk's head tucked under his jaw and face buried in his thick sweatshirt as the skeleton's arms wrapped around the child's tiny body.

The two stayed like that for a while, Sans gently carding his fingers through the child's short hair, careful not to catch it in the joints of his bones, and Frisk focusing on breathing through their hiccuping sobs. Sans wasn't exactly warm, still far too cold to pass for human in temperature, but he had an energetic sort of heat that radiated from his bones. Frisk idly noted it must be his magical ability, taking in another calming breath and finding comfort in the skeleton's unique smell.

Sans smelled like early morning fog, Frisk thought, when the sun was just rising and rain had fallen the night before. It was a crisp and clear, yet somehow dry, smell with strong undertones of magic, something that fascinated the human child to no end. Frisk often found themselves struggling to place the magic smell that surrounded their monster friends into words.

They were startled out of their thoughts when Sans shifted, moving so he was lying fully on the couch, instead of slumped into the cushions, and using the arm as a head rest. Frisk kept their place curled on top of him but finally freed their face from under Sans skull, turning their head to the side to let their cheek rest on his sternum- listening to the constant thrum of energy that replaced a heartbeat in his chest. It was quieter and more controlled than the sound Papyrus had.

"You smell funny." Frisk finally mumbled, smiling when the remark made Sans snort good-naturedly, his bones making soft dull clacks muffled by fabric as the motion shook his body.

"What do you mean I smell funny? If anyone smells funny around here it's you, fleshbag." Frisk giggled at his words, feeling his low voice vibrate though his bones before moving to lay with their chin resting on folded arms and looking Sans in the eye. His features were soft and fond as they took in Frisk's blotchy red cheeks and tear-irritated eyes, hand still slowly running through their hair comfortingly.

"I think it's your stinky magic." Frisk hummed with a small smile, pleased when Sans snorted again, before adding, "Besides you don't have a nose so how would you know?" This time the monster gave a full laugh, eyes closing with the force of it and smile widening.

"Ah, I guess you got me there bud." Sans admitted in exaggerated defeat. But after a moment of companionable silence his grin faltered some, expression sobering, and Frisk knew he was still waiting for an answer.

"Some kids shoved me today," skeletal hands stilled in their comforting strokes, "They've been bullying me for a while now." Frisk continued, their eyes closed as they spoke. "It's always been just words, and I never payed them any attention so I didn't bring it up earlier. But today they actually pushed me and when I fell over I hit the corner of a desk." Eyes still closed, Frisk waited for a reaction, taking note of how still Sans had gone and that the thrum in his chest was louder now.

"They hurt you." It wasn't a question by any means but Frisk answered it anyway, trying to ignore the dangerous edge in Sans's normally mellow voice. If they didn't take it as a threat then maybe it wouldn't become one.

"It's just a bruise, it'll go away soon." They whispered with a small shrug, trying to ease the agitated monster's mood, listening as the thrumm! grew even stronger still- making the air buzz with magic. Frisk opened their eyes to see Sans glaring at the wall, the lights in his eye sockets flickering like blue flames, and even though the skeleton's body was otherwise still and lax, the dark anger Frisk saw on his face was enough to make them sit up sharply in alarm.

Agitated blue eyes trained on Frisk when they moved, the dangerous anger bleeding away as Frisk's small hands rested on either side of Sans's skull. Child and skeleton sat, staring intently at each other, Frisk watching with no small amount of relief as Sans reigned in his powers, the buzz fading from the air and his eyes dimming once more.

"Can I see?" He eventually asked, voice uncertain and still harboring hints of his previous mood. Frisk nodded and moved to stand facing away from the couch, tugging the back of their sweater up just high enough for Sans to see the bruise on their lower back. He sat up straight and waited until Frisk gave a soft "okay," signaling he had permission to inspect their back.

The skeleton hummed thoughtfully, hesitantly tracing a single finger over the wounded area as though afraid Frisk would break if he touched them. "I might be able to help a little," he murmured, more to himself than to Frisk, "I don't know much healing magic and it's mostly for bones..." He trailed off, thinking again before stating more certainly, "Alright, hold on."

Frisk waited patiently as Sans carefully placed his hand over the bruise, ridged bones resting as gently as possible over the deep purples and greens staining the skin of their back. The buzz from earlier permeated through the air, this time more focused and dense, and a tickling sensation danced though the muscle and skin of Frisk's back. It sent chills rolling up their spine, the feel of magic foreign and odd, though not exactly unpleasant.

When Sans took his hand away Frisk let their clothes drop back into place, turning around again to judge the monster's mood. He looked more relieved now that he had helped, though his shoulders were still too high and tense- pushing the hood of his jacket up to rest just below his cheekbones.

"All better?" They asked, voice purposefully light, but Sans only frowned and dropped his shoulders, all the tension seeming to leave his bones simultaneously, only for the rigidness to snap back into his posture a heartbeat later.

"No Frisk, it's not all better." He replied, bringing a hand up to drag down his face, his bones making a faint scraping sound against each other. "They hurt you and that's not okay. They can't get away with this." Frisk silently watching Sans slip back into his anger, bony hands forming shaking fists in his lap as he refused to look at the child in front of him, eyes once again sparking. The ten year old had never seen their skeleton guardian so angry and grew nervous, knowing they didn't have a clue how to help Sans calm down.

Frisk knew how all their friends' anger worked, in the relatively short time they'd known Undyne, Toriel, Papyrus, and the others Frisk had seen them all lose their temper and knew how to act accordingly. But Sans was a completely different story. He never got angry- or if he did, he was extremely good at hiding it.

Tears threatened to spill down Frisk's face for the third time that day, unwilling to accept that Sans's anger was actually rather frightening and was making them nervous. There was something darker and more deadly about his fury than even Undyne's. Their shaking shoulders attracted Sans's fiery gaze, the skeleton doing an almost comical double take when he noticed the child in front of him was crying again. Eyes softening, Sans took a deep, lung-less, breath and forced himself to calm once more.

"Sometimes I forget you're only ten," He murmured, pulling Frisk close in a hug- this time to comfort both them and himself. "You've done so many amazing things and you're so strong that I just forget how young you are..." His deep voice trailed off for a moment before he pulled away from Frisk, just enough to look at their messy face, only the smallest traces of anxiety and fear seen there.

"I want you to call me the next time this happens okay? And I want you to tell an adult at school too." Frisk nodded, using one tiny fist to scrub at the tears and snot on their face. Sans winced a bit, laughing softly as he took their other hand with a tired shake of his head.

"C'mon kiddo, lets go get you cleaned up and start on dinner, Pap should be home soon."