Slash!
"heh, didja really think you'd be able to-"
Sla-
Sans saw the double slash - no time to dodge. "I'm dead," he thought-
When the battle haze cleared, Frisk was posed with her knife almost touching him, struggling against...something.
She backed up, eyes red but glowing with a strange yellow light that started emanating from her in blasts. Sans backed away from her, wondering...
The yellow rays exploded from her and somehow she split into three people, the largest in the center.
The normal Frisk was on Sans' right side, and a girl in a green sweater on the left.
In the middle, there was an older girl with a cape. She got up and extended a glowing blade from her right hand, looking at Sans directly. He braced to dodge and prepared for battle.
But instead, first she turned and stabbed the girl in the green sweater through and through. Sans couldn't tell if it killed the girl or not. Then she put away her weapon and turned to Frisk, grabbing her by the sweater and pulling her upright. She looked carefully into her eyes, then let her go and turned to Sans. Frisk started crying out of shock, turning away like there was nothing left in her in terms of energy.
Sans and the older girl regarded each other for a minute. He marked how she looked calm, but with no malice... not like the red-eyed Frisk he had just been fighting.
"So..." he said. "That was weird. What are you anyway?"
She looked slightly ashamed. "I'm ... a player."
"What?" he said.
"I took over control from another player to stop you from getting killed," she said. "It's a long story."
"I see," he said. "You want me to think you're not the same one who's been killing everyone?"
"I'm actually not," she said.
He was looking at...something. Suddenly she realized.
"I didn't think I'd actually have a level here," she said, surprised. "Are you reading it?" she asked.
"ROSE. LV 1000. EXP 1000000. Is happy you are alive," he was reading.
His eyesockets went dark. "YOU'VE KILLED A LOT HAVEN'T YOU..." he said.
She winced. "You really are amazing," she said. "I really didn't think it would show..."
"WHY . . ."he asked. Frustration over the resets was overwhelming, and now finally this could be the answer he had been looking for all along. Why Frisk could be so different depending on the run. Why there were "save points" and "resets". She called herself a player? He was starting to get an inkling of what was really going on. Was this person the real "anomaly"? Was that why they had so much LV?
He attacked with lines of bones, and then as she dodged, with Gaster blasters. She blinked out of sight for a few seconds, and he saw Frisk and the girl in green - Chara? - disappear. Then Rose was back.
She dodged skillfully, almost as if made of air. She made no attack at him herself, only watched with sober eyes and weaponless hands.
They fought for a long time, or rather he fought and she dodged.
"WHY . . ."he kept saying, and every time he said it, her eyes looked a little sadder. She got slower.
"YOU SAID YOU ARE A PLAYER... IS THIS A GAME TO YOU?!"he yelled, putting everything into a massive attack.
His words made her stop, and she seemed to resign herself with getting hit with the attack, determined to take it all as a kind of penance or apology.