(A/N Thank you so much for three readers! It may not seem like much, but it means a lot. Thank you to Winterfurr for your lovely comment, I'm posting this chapter for you! Your comment literally made my whole day, so thank you. I'm out of prewritten material, so give me some ideas! Thank you again and enjoy the chapter!)
(Gaster!Sans POV)
I storm into the prison, my team of monsters behind me. I use my Gaster blaster to shoot down the big metal door. We storm in the prison guns blazing.
"Let's look around." I say once we know everything is safe. I find a desk with lots of notes and letters. There is a calendar hanging on the wall in front of the desk. A date is circled in red pen. It's marked on the Thursday of this week. It's Monday currently. The date on the calendar is marked "Execution Day". I decide to look through one of the notebooks among many.

Day 1: subject #273
Info: the subject seems scared. 273 is scared of my presence and will not eat or drink when I offer it to them. I hope they become better adjusted to their new surroundings.

I flip through the notebook. They all are about the same, just quick updates on an unknown subject.
"Hey guys!" I say to my band of monsters. "They have been doing tests on subjects here, let's look around to make sure we can save as much people as we can." I tell them and we split off to look around.
I come across an area with lines of steel doors. It's quiet. The doors each have a clipboard next to them. Most of them star that the subject was terminated, except one, 273.
"BACK AWAY FROM THE DOOR IF YOU WANT TO LIVE!" I tell and raise another Gaster blaster out of the ground and send the thick metal door off its hinges. Dust flies when I blast down the door. I make my way into what seems like a cell.
"GET AWAY FROM ME!" A female voice yells at me. "I know who you are! Please don't hurt me." She says curled up in a corner of the room.
"Dove, we've never met-" she cuts me off.
"Do not call me that! I know clearly who you are! Don't play stupid with me Gaster! You killed Glenn!" She screams.
"Woah, woah, woah. I never killed anybody. You've got the wrong guy. First, I ain't Gasta', he's my fatha'. Second I'm here to get you out of here sweetheart." I say and stick out a hand to her. She slaps it. I see genuine fear in her eyes. She really is afraid of me.
"Stop playing stupid! You are Gaster! You look just like him! You're here to kill me." She yells at me again.
"You have left me no choice." I say and telekinesis her in a yellow aura.
"Put me down!" She screams.
"Damn you're a loud one." I tell her. She pouts and turns away from me. "Honey, you've got to believe me! I ain't Gasta'. I'm not here to hurt ya, I'm here to save ya." I tell her and teleport back to camp.
I found a nice cozy room for her to stay in. It was a blue and white walled room with a nice bed and desk with a turquoise carpet in the middle of the floor that covered most of the dark wooden floor.
"Here is your room, sweetheart." I tell her and walk in the room and lock the door behind me. I gently rest her on the floor and she scrambles away from me and hides under the desk.
"So how did you get there sweetheart?" I ask her.
"First, I'm Aqua, and why do I have to tell you Gaster? You should know already, you're the one who put me there!" She starts to yell again.
I feel Gaster's presence in my mind.
Yes, she is right I did put her there
Dad! What the hell did you do! You basically ruined her life! You messed up her head!
Gaster tells me what happened
I know you needed that experiment for your boss, BUT THAT DOESN'T GIVE YOU THE EXCUSE TO MURDER PEOPLE!!! After saying that I realized I said it aloud.
She cocks an eyebrow at me.
"Sorry I was talkin' to someone." I tell her. She continues to cock an eyebrow at me.
"So basically I'm Gaster Sans. Your famed Gasta' character can talk to me through my mind. He's my dad. He told me his side of the story, and I'm siding with you Aqua." I tell her. She smiles weakly at me. She is starting to warm up to me a little. I don't dare go closer to her. I just wink at her and unlock the door and close and lock it behind me.
(A/N sorry this was a little short, ran out of ideas, please let me know of any ideas you guys have, because I'd love to hear it! Hope you liked the chapter and see you later! Bye!)