Swapfell! Sans x Reader A tsundere's love (Completed)

chapter 1: A new face

You run to meet up with your friends. You were running late even by Sans' time. You'd overslept by an hour this morning.
"Stupid alarm not going off….." you mumble as you slow to a jog stopping for a moment before entering the park. 
Sans, Paps, Blue and Swapy were waiting for you. To your surprise there were 3 other monsters there. One was Red, and another Edge but the third one you didn't recognize. He was obviously another Sans, slightly taller than Blue, but dressed like him. Armor and all only a darker blue he has a scar over his right eye. 
Red notices you walking over and tackle hugs you. "(Y/N)! You're here!"
"God, Red, that's disgusting." Edge mutters but you don't mind. Red is one of your closest friends after all and you love his hugs.
"Ha, you had us worried, kiddo" Sans says. "I'm usually the one who's late" 
You let Red go and sit between Sans and Blue. "My god damned alarm didn't go off."
"Aww, well that's sucky." Blue says before hugging you. "Oh, I'd like to introduce you to Viper. He's from a swap universe like me. But its kinda like Red and Edge's too. Its called-"
"Swapfell. As Blue said, I'm Viper. For some god forsaken reason I'm his friend. But I guess its nice to meet you." Viper scoffs at the end like he really didn't mean it.
"Um… hi? I'm (Y/N) it's nice to meet you. Are you guys coming to see the movie with us?" You ask the three fell monsters. "We're going to see Birds of Prey."
"Unfortunately me and Red have work today. Some other time perhaps." Edge said. "We'll see you later."
"Later kitten." Red says before hugging you again and leaving for work. 
"What about you, Viper?" Paps asks him.
"Sure. Just don't stick me next to her."
"Viper that's not very nice." Swapy said. 
You look down and fold your hands in your lap. Did you do something to upset him? You don't remember doing anything like that.
"You know what, I'm not feeling up to going out today…" you say. "I hate to do this to you guys…" you pull up the hood to your black jacket with (F/C) trim. You didn't want them to see the empty look in your eyes.
"You okay kid?" Sans asks you softly and all you can do is shrug. You wanted to go out but didn't want to upset anyone.
"Viper, that was not very nice of you. This is the first time in weeks we have gotten her to come out of her house." Paps says to him.
You have pretty bad depression and anxiety. It makes it hard for you to be around people but you are a novelist for work. You met everyone when you were writing a book on a monster falling for a human. You did a lot of research on souls and if humans are compatible to be with monsters. It turns out they are.
"Yeah, Viper! She works so hard and you are rude to her." Blue said. 
"Enough boys… I'm going home…. who knows,  maybe I can get some work done on my next book…." you say before getting up.
"Hey!" You glance over to Viper who had spoken up. "I didn't say that to be rude. Hell it's not 'cause I dont like you either it's just….." he stops for a moment to think. "I'm just not good with new people." He mumbles.
Your lips twitch up for a moment. He seems honest enough but still, your mood has been ruined. 
"Thanks but… Shit's happening and I'd rather not be out right now…. later guys…" you turn and make your way back to your house