The worst way (gaster Sans X reader)

Pain.

It had been a week since Frisk and G came to school with me.  Frisk had started receiving bully's, but they always backed down when they saw me. And G tried to help, but it usually just ended up with him in the office. G and I were NOT getting along. We fought over everything and anything. He would say something, I would respond with a snarky comment, he would snicker then make a comeback, and so on so forth. We even got in a fist fight one time in pe. And now it was Friday, and G and I were in PE. We were doing boxing as a lesson. My favorite.
"Partner up" said the pe teacher. Of course I rushed for my friend, but the teacher stopped me "actually [Y/N], could you partner up with G? I don't want him hurting anybody, and he seems passive aggressive towards you." I sigh.
"Yes sir." I say. I look at my friend apologetically, and she mouths 'I feel so sorry for you'. I mouth back 'me too' we both laugh. I turn back and walk towards G, who is leaning against the wall.
He looks pretty good in the pe outfit...
STOP IT! I can't be...ugh. I walk over to him.
"Teach wants us to partner up. He's afraid you'll hurt somebody~" I tease. He rolls his eyes.
"Whatever." I snicker, then walk over to the practice mat.
"So you know how to box?"
"Well I know how to punch doll face."
"Oh really. Wow I'm so impressed. Throw a punch my way." I say. He does as instructed and I easily dodge. "Is that seriously all you-" I am cut off by him wiping me off my feet.
"Don't get distracted dove." He snickers. I stand up, rage evident on my face.
"Oh no you don't." We start to spar. I knock him down, and he pulls me down with him. I kick him in the ribs, he socks me in the stomach. But we both keep getting up. Everyone in the classroom is watching. I punch him in the jaw. He swings back, but I duck out of the way.
"You really are an ass, attempting to punching a lady."
"Oh your a lady? I couldn't tell by the way you dress!" He shoots back. I scoff and knock him off his feet, pining him down.
"Asshat."
"Bitch." I push his head down farther into the mat.
"You know, I would really enjoy this position if I were facing upwards, and you were moaning out my name~" he coos, and I release him, pushing myself off of him. I launch backwards onto the mat, ass first, sitting about a foot away from him, surprised.
"R-really?" I whisper.
"Ch, no." He says getting up. "Just needed to get you off of me." He says dusting himself off. I look down, embarrassed.
"Awe, what's wrong? Did the little dove think I actually liked her?" I look down, more ashamed then ever. "Tch, your just a toy to me."  I stand up, shadows covering my face. I look up at him, tears in my eyes.
"Your playing with my emotions. Stop." I say. Everyone else looks at me shocked. They haven't seen me like this since.... I ignore them, and peruse G. I grab him by the shoulders, to hold him in place, and quickly lift my knee into his crotch. He yelps in pain, and falls to the floor. Everyone in the gym gasps. I raise my foot and place it on his skull, ready to stomp down and crush it in an instant. I've done it before, it wouldn't be ha-
Stop.
I realize my actions, and turn and rush into the locker room. I undress quickly back into my jeans and sweatshirt. I grab my keys and rush out of the locker room the back way. I walk around to the front of the school, and into the office.
"Frisk were leaving." I say to her.
'[Y/N] what's wrong? Your eyes are red and you have bruises. Have you been crying?'
"It's nothing. Let's just go. " I say rushing out of the office. I go to my locker in the hallway and grab my phone and car keys, my school keys already on my lanyard around my neck. Frisk walks up behind me. 
'Where is Sans' she signs.
"In the gym crying most likely."
'What?!' She says.
"I kicked him in the crotch. Don't worry about it. I'm sure he'll find his way home." I close my locker shut, and rush out the front door to my car. Frisk is rushing after me, trying to keep up.
'[Y/N] I don't think we should leave him...' Frisk signs, and I sigh.
"We'll wait in the office for the rest of the day for him." She gleams happily and rushes up to me giving me a hug.
"Thank you." She whispers. I nod, patting her head. We walk back inside and to the office. I plop down in the chair, and the secretary at the front desk looks at me.
"[Y/N]? What are you doing out of class?"
"Oh. Well it was close to the end of the day...and it happened I guess. I was loosing my composure."
"Oh. Well, you are welcome to leave class anytime that happens. But please let us know."
"Sorry i just, I just needed to get out of there." I smile at her. Frisk tugged at my jacket, and I looked at her. She signed
'What does she mean' I sigh.
"Frisk, sometimes I get angry. And when that happens, I 'slip up'. And I can be dangerous to those around me-" I was going to finish but the door to the office burst open to G, walking in. Frisk looks at him, and smiles, but I look behind Frisk still. I sigh.
"Well. Are you ready to go?" Frisk look at me and nods, so I stand up, my car keys in hand. I walk up to the front desk, and whisper something to the lady. She smiles and nods when I finish.
"Sure thing. I'll leave a note in his office for him."
"Thanks." I turn, and walk out of the office. I catch g sending a glare my way, but I completely ignored him. Frisk gets up and hurries after me, and I hear G sigh and follow after me and Frisk. We make it to the parking lot. Get in the car, and drive off back home. In complete silence. As soon as we do make it home, I immediately get out of the car, lock it once G and Frisk get out, and rush inside to the kitchen. I open up the fridge and grab some of my vanilla milkshakes, then I rush up stairs to my room. I throw my car keys onto my desk, along with my school keys. I keep my phone and grab my speaker. I change out of my jeans and t shirt, into some shorts, and a sports bra. I tie my hair into a ponytail and go to my bedside table looking for my punching gloves, only to nit find them. I sigh and leave without them. I go into the exercise room and place the milkshakes into the mini fridge. I turn on my speaker and link it to my phone, and start playing my music. After looking around the workout room, I find my gloves on the table where I bandaged myself last time. Lastly, I go over to the door and lock it. Then I turn to the punching bag.