Sans had always been a good kid. When his father was at work, he'd bring him food. He helped his mother until she died. He loved taking care of his little "smile noodle," which was his baby brother Papyrus. Now Sans was 12 when his mother died, leaving his Royal Scientist father Gaster, at age 32, and his 2 year old brother behind. Sans loved taking care of his brother. Though he loved science and working with his father, Papyrus seemed to always try to cheer him up.
Sans and his family lived on the outskirts of the Underground. In a little town they called "Snowdin." (Mainly because when they first set up houses, everyone got snowed in due to a monster putting snow in front of everyone's doors.) Sans would watch his father on very few occasions leave to go to the capital via taking the river person's boat through Hot Land. It would take a while longer than his usual times though. 7 different, abstract times. It didn't help that at those same times Papyrus pointed from his crib to see Royal Guards swarming the town.
It was every child's dream to either be in the Royal Guard, or become a Royal Scientist. Sans didn't really fit in with those crowds. All he wanted to do was take care of his baby bro. Don't get him wrong, he knew a lot about the different sciences due to his dad, but Sans felt joy in little children and their laughs.
Sans had just turned 16, 6 days ago. 16 in monster years. Now he would officially stop aging. Well, at least until he had a kid or married someone. He sighed. Gaster was very excited and wanted to set him up with one of his students. A nervous, yellow, reptilian monster named Alphys. Though Sans had already met her and he knew, she didn't sway that way.
He went out into the forest where the "Doge" Royal Guard were stationed. He kept walking, solving puzzles, until he came across a game of "Ball." He'd heard of this game. He began pushing the snowball around until he got it into the hole. It took a few tries, but when he finally got it in, a red flag popped out of the hole. It had an inscription on it "Try as you might, you continue to be yourself." Sans sighed and walked along.
On his way there he saw a bipedal taller dog and a quadruped dog running around a snow sculpture he was creating. Sans saw their necks getting longer and then knew the species of Doge monsters they were; Lesser Dogs. He kept walking, didn't know how long, trying to get the idea of being forced together with someone in order to age. Why did Mother Nature make them this way? He bumped into a large, purple, door. He traced his hand around the handle, before pulling it open. It led to a large corridor leading south. He took it until he had to turn west. He headed up the stairs to find himself in what seemed to be a cozy, broken down, little home. Outside a rotting door, he hear crazed laughter and crying. He slammed to door open to see somthing green retreating underground and a bundle of blankets. Instinctavly, his magic kicked in and he grabbed onto their soul to stop the body from falling.
He gently floated the precious bundle over to him to see what it was. It was a pinkish face of not a monster, but of a human. Judging by the cuts, blood, and barely any bruises, Sans knew this was the work of a plant-like monster. The pathetic creature let out a whimper. "shh," Sans comferted. "everything's gonna be alright," he remembered the nickname his mother called him and Paps, "baby bones. i promise, i'll protect you."
Sans had remembered that Humans needed names. "Baby Bones" didn't seem to fit a human… "i'll protect you, corsiva." He told the baby with the cherry red soul.