It's Not Like I Like You(Abyss!Sans X AU!Tsundere!Protector Reader)

Chapter 2- Part II- Mission

Y/n's aplomb movements halted suddenly and Abyss stared at her in slight concern.
She swiped open a portal, seeming panicked for a second.
"No matter what you do, don't come outside. Stay away from the windows.
I have to go do my job."
Without waiting to hear what Abyss said in return, she left.
Y/n carefully lept down from the portal, and immediently faded herself to the pitch black castle color.
She started walking stealthily, going the way to the dungeon.
After many infilitrations without Nightmare and his team knowing, she had memorized almost all of the place throughout.
She succeeded, going past the Papyruses and Cross, who happened to be eating chocolates in the kitchen.
The female carefully opened the dungeon door and crept silently downstairs.
Y/n paused. Strange. The voices were particularily silent after she left her home.
She spotted Dust and Killer were guarding one of the many cells, most likely with Outer in it. Killer was the one who was guarding and Dust was occupied with sharpening his attack bones.
She slid into a battle stance, ready to lunge, if necessary.
Having fought both of them in the past, Y/n knew that  they could easily detect her overwhelming presence soon.
The only reason why she was still not captured yet was because of the years spent on sparring and escaping.
However, the thunderous sound of gaster blasters being charged upstairs got the duo away from the cell.
No time to question the event.
Y/n ran to the cell and kicked it open with added strength.
Outer was knocked out cold, being shackled to the stone wall by his limbs.
She quickly morphed into her sword form, and quickly, but carefully as to make sure a body part was not going to be chopped off, smashed the shackles.
Outer sank to the floor, and Y/n morphed back, carrying the knocked out skeleton.
The protector ran out of the dungeon, to see a chaotic scene.
The Star Sanses were fighting the Bad Sanses, but no one has noticed her yet.
Dream was busy fighting Nightmare, deflecting his blasters and moving out of his tentacles' grasp and Cross's knives.
Ink was slashing red paint at Error and Killer, dodging their attacks of strings and knives.
Blueberry was blocking Dust's quick stabs, avoiding his gaster blasters and firing beams back.
Everyone was distracted.
Y/n quickly opened a portal, but the sudden flash of light and sound alerted Killer, him being the closest to her.
His head turned to her direction and he shot knives at Y/n.
She was holding Outer, so she threw him in and closed it with a swipe.
She quickly moved out of the way, but one of the knives stabbed into her shoulder. With a wince, she summoned her weapon in her good hand, and Y/n deflected the incoming wave of knives and swung it at Killer.
Killer had to teleport out of the way, but the weapon flew back and he sidestepped it.
When Y/n blinked, he was gone.
Gripping her weapon tightly, she looked around the area, waiting.
Killer appeared and attempted to stab her, but she blocked it.
The two fought viciously.
Y/n failed to notice Ink sneaking up on her, and he swung his paintbrush down.