Forever together...Sans x Frisk fanfic

How could you have done that?!

Sans' POV
(btw today is Sans' birthday, Frisk remembers it only when she wakes up, this is very important)

I woke up in an unknown room, then my head started to remembering...Frisk asked me if I could stay with her for this night, so we slept together...I got up and went in the kitchen, and I found Dad...hey, he seemed a little worried...

Sans: Hi dad

Gaster: Hi Sans...

Sans: Dad, what's happening? You look like...*sigh*something's troubling you, am I right?

Dad:...

Sans: You know who's behind Chara and Asriel's situation, right?

Dad:...

Sans: I take that as a yes...*sigh* Dad, I'm your son, you can tell me everything

Dad: If I'll tell you, you'll be angry...

Sans:.......I promise I will stay calm

Gaster: behind Chara and Asriel's situation there's...your mother...

Sans: What?!

Gaster: It all started when we left this city...

flashback

(only for now, Gaster's POV)

an important man of another city asked my help for an experiment, I couldn't leave you, Papyrus and Arial alone...Arial was your mother, she was kind, sweet, and very, very strong...like Frisk...anyway, I had to bring all of you three with them...Arial was angry with me, she knew about Frisk, because it was her that accompanied you from home to school and from school to home, you too always stayed together...anyway, when we got in the other city, Arial was angry with me because I was doing too much experiments and that I had to stay more time with you and your brother...the day she disappeared...she was going out for buying something, but when she got out, I texted her, telling her that I would be taken by an experiment...you and her were the only ones that could teleport, you got that ability from her, she went in my lab and...we had a discussion...one of my experiments that changed personality finished on her, and...she changed...I had to put her in a special dungeon where she couldn't teleport, she was a treat now for you...the day we left and returned here...it was the day when she changed...

Sans' POV

I had no words...why? And plus, why I don't remember her?

Sans: Dad...why...I can't remember her?

Dad: I had this machine in the other house, that makes people forget about something that we can choose...

I couldn't hear anything of this anymore, and I left...first of all, I went to see how Frisk was going, if she was awake or if she was still asleep...I looked on her, and she's still asleep, I sat down on her bed and played for awhile with them...Frisk moved a little and smiled...I gave her a kiss on the cheek and left...

Frisk's POV

I woke up a few minutes ago, because I heard someone walking...the smell of ketchup...heh, Sans...I'm gonna make him think that I'm still asleep, like I did with mom when she went all days for waking me up and go to school...he started playing with my hair, I moved a little my head and smiled, he gave me a kiss and he left...I decided to got up, because today it's his birthday, I remembered just now, fortunately I have the right present...

I went in the kitchen and found Gaster...! He was crying! I ran in his direction

Frisk: Gaster! What happened?!

He looked at me, but he started to cry even more...something just happened with Sans. I ran out of the house, I saw him walking away. I tried to run but...what I saw now gave me desire to kill...THEY were in front of me...I ran in the house, took a knife and went out...oh no...they were walking in direction of Sans. I started running in their direction and stabbed them in the back...I screamed when I stabbed them, so I could give Sans the time to run away

He turned around his face and saw that I stabbed them...he was disbeliefed...what?

Frisk: SANS! WHAT ARE YOU DOING? RUN!

Sans:......Mom...

What? This one with the cassock is...Sans' mother?

She teleported away...Sans' legs were shaking for a moment and then he fell. I ran in his direction

Frisk: Sans I'm so sorry I didn't know that was your mother I thought it was the one that brought Chara and Asriel away...

Sans: FRISK! *cry*

He hugged me tighter...I'm so confused, but I slowly hugged him back...

Frisk: Sans, I think you should tell me everything...