You may not have a support system right now, and that’s okay. Keep a journal, vent on the internet, scream at the sky. Someone is listening, someone hears you, and I promise someone cares. Love yourself the way you wish someone would love you.
So Underfell Sans (the grumpy, cold and agressive version) and the reader get out of the Underground. The night falls, and she convinces him to come with her, and she takes him to a really good spot to see the stars he have never seen before. He have a crush on her and maybe let the cold facade down for once. I don't know if it would make a great story, take liberties if it's too restrictive, but have fun writing this !You're talentend enough to make it works, anyway ! Take care of yourself <3