It's been about 5 years since the Monsters came from the underground. Everyone has more or less accepted them, given that Monsters are way more powerful than humans that is. The most powerful Monster are called Boss Monsters, and only a few are alive. You happen to become best friends with one of the most powerful Boss Monsters in the world, Sans. He is second in line to king Asgore when it comes to strength, but has the most powerful magic known to humans and Monsters. You have been best friends with him and his Monster friends for a good two years now.
Even with him being so strong, and scary, your not scared of him! Being best friends with Sans is fun, you both like almost the same things and love all types of humor. You two become extremely close and everyone can see this. It's no surprise when you start developing strong feelings for him. You just can't tell him. No matter how much your and Sans’ friends try and get you to confess to him, you just can't. You don't want to ruin your friendship with him!
It hurts when Sans starts to date a human named Misty. She's sweet and seems to make Sans happy, so you don't get in the way of their blooming relationship. You start to notice Misty doesn't like you hanging around Sans all the time and you start to see less and less of your best friend. You tell yourself this is normal and don't think anything of it.
You are on your way home from work one day, when you see Misty with another human guy heading out of a motel. You confront her and find out she has been cheating on Sans for a while.
How will this all end? Will you tell Sans on what you saw and risk his happiness, or will keep quiet?
(A/N): This will be just a short story with underfell Sans. I hope you all enjoy and have fun on the ride. It will be 5 chapters long and each chapter will be about 1000 or more. Please take the time to read my main fan fic: Broken Souls; a reader insert with the original Sans.