Gaster decided that if the best part of Sans' Soul being partially Pure was that he could love again, then the second best part was his willingness to cooperate.

Because now that he had a friendly disposition towards Gaster, he was actually optimistic and eager to answer any questions Gaster might have, or participate in whatever experiment Gaster had cooked up to learn more about the Corruption.

Granted, he still complained. He complained a lot, but he didn't really mean it. Well, actually, he probably did, but it was all more or less in good nature.

And, of course, this came especially in handy since learning of Sans' ability to mix Pure and Corrupt Magic. They spent a good week or two trying to figure out a safe way to do that, until Sans eventually passed out one day and couldn't move without puking for the next two days.

But he had still participated in that eagerly. Never once did he resist doing something because it would help Gaster.

He also continued to call Gaster "Dad". That was, shamelessly, Gaster's favorite part of it all.

Today, Gaster didn't have an experiment, so much as a question. And, admittedly, Sans might very well decline to answer, as he had before, but Gaster was still curious.

So, instead of going to the lab with Sans, he led his son into the living room, and sat down on the couch.

Sans sat next to him, looking slightly concerned. "is... is everything alright?"

Gaster blew out a breath and nodded. "Yeah, just... Sans, I have a question for you. And, I realize that... it maybe is... a little difficult, and you don't have to answer, if... if you don't want to."

Sans just looked at Gaster. "... okay...?"

Gaster hesitated a moment. "What... What happened?"

For a moment, Sans just looked at Gaster, confused. But, as realization dawned across his face, he shrank back. His arms pinned to his sides and his shoulders hunching, he pulled back in a subconscious effort to hide away from the world.

Gaster reached out, grabbing ahold of one of Sans' hand. "It's alright, Sans. You don't have to talk about it. I shouldn't have asked."

Sans closed his eyes and took a deep breath. "n- no. i... i'll... i'll tell you. i- ... i just need a couple of minutes. and-..."

"... Yeah?"

When Sans looked up at Gaster, there was a sort of desperation in his eyes. "...and promise me you won't tell papyrus about this. ever. i- ... i think... it would hurt him, and..."

"I understand. I won't tell him."

Sans nodded slowly, took a few deep breaths, and began.

⎰Prior to This...⎱

Sans became aware slowly.

It couldn't be said that he woke up slowly, because he wasn't sure if he was awake. For one thing, he was completely blind, in darkness. He couldn't even tell in his eyes were open or not. For another, he seemed to recall taking copious amounts of damage and receiving a massive number of wounds, which said that his body should be screaming in pain, but he could feel nothing. That wasn't just saying he wasn't in pain, he literally could not feel anything. When he tried to move, he couldn't tell if he had succeeded. On top of that, he couldn't hear nor smell nor taste anything.

So, essentially, he was aware of his own consciousness, and that was about it.

He couldn't exactly remember how he had come to be this way, either. He could remember fighting in Waterfall, telling Undyne to get out...

Knowing he wasn't going to come out of that alive, and deciding that he might as well use as much Magic as he could, kill as many Corrupters as he could, before he went down.

And then...

And then he had Fallen Down.

And now he was here. Wherever "here" was.

How long he had been there, he couldn't say. The same went for how much longer it was before anything happened.

It was so subtle, so gradual, that at first he didn't notice.

A distant hum, the rise and fall of a voice, speaking.

Eventually, he recognized it for what it was, and it seemed as if the more he focused on it, the louder it became. After a little while, he could even recognize a few syllables here and there.

With the sound, a dim light finally reached his eyes, and he was suddenly aware of how much everything hurt.

He groaned. The voice stopped. After a moment, it started again. It sounded like it was asking him a question, but he still couldn't quite hear clearly.

For a moment, he struggled to sit up and rub his eyes, but found quickly this was futile. He still couldn't move; his limbs felt like they were weighted down.

And gradually, his senses sorted themselves out. He was lying on his back on a flat surface. Above him, the ceiling seemed to be made of a pale, purple-pink plaster type material. The room smelled of disinfectant, that kind of hospital-y smell, but there was something a little unsettling about it. It was also relatively cold.

He tried to move again, and failed again. He realized he was strapped down.

The voice started again. It was high pitched, friendly. "Well? Are you awake yet?"

That voice scared Sans.

He stuffed that fear down, though. "... who...?"

"Oh! How silly of me. I haven't introduced myself, and you can't even see me, can you? Hold on, just a second."

And then, there was a flower.

A smiling flower.

Sans was now thoroughly terrified.

"Howdy! I'm Flowey, Flowey the flower!"

"heya, flowey the flower. i'm sans."

"Oh yes! I know that! I know that just like I know you're my opposite, Commander of the Pure army!"

Sans felt another stab of fear. This flower was commander of the Corrupt army.

"ooooo-kay, so, what'm i doin' here?"

The flower's grin widened. "You're here to help!"

"if by 'help' you mean 'kill you all and win the war,' i agree."

Flowey laughed. "Ha! No, you silly goose! You're here to be the best Corrupt weapon there ever was!"

Sans frowned. "sorry, but i'm afraid i have to decline. y'see, i'm a pure monster, and i rather like it that way. and pure monsters don't fight for the corrupt, so you see, we have a little bit of a dilemma."

Flowey didn't just laugh, he cackled. "Oh, Sans! You didn't think you had a choice, did you?"

Out of the corner of his eye, Sans saw what appeared to be a vine, presumably under Flowey's control, twisted around a syringe filled with something dark.

Sans sighed. "well, it was worth a shot."

Flowey snickered. "Puns won't save you now, you smiley trashbag."

And then the vine whipped the syringe forward, plunging it between Sans' ribs. In a matter of seconds, Sans went from feeling slightly cold to burning hot to subzero freezing.

That was nothing, though, compared to the pain.

He had already been wounded, that much he knew. But now it felt like the Corruption seeped out of his Soul and wormed its way into his injuries. It burned worse than pure alcohol in a cut, and felt like it was slowly pulling him apart.

He couldn't even scream.

He could do nothing.

Nothing, as his body contorted against the restraints of it's own accord. Nothing as his Magic was slowly strangled out of him. Nothing as the Corruption spread through his body.

Nothing, nothing, nothing.

As Flowey bobbed in and out of his fading vision, laughing in a voice that just pierced the fog gathering in his skull.

Nothing at all.

~o0o~

"Golly, you really are strong, aren't you?"

That was the first thing he heard when he woke up.

Sans opened his eyes. He was still in the Ruins, still strapped down to the table. Everything ached, but he found that he could think rather clearly, and he still was quite adamant about fighting for Corrupters.

He also found that some of the restraints had been undone. He couldn't really do anything, but he found he could lift his head a little. He did so, and looked at his chest.

His ribs were covered in half-healed wounds, hairline fractures spanning across nearly his entire chest. In his ribcage, his Soul still beat strongly, still Pure white.

"oh," he said, half for himself and half in hopes it would annoy the flower. "well, i'll say i'm pretty releafed that didn't work."

Flowey slipped into his view, giving him a sidelong look. "That wasn't funny."

So, then, he didn't like puns. "i dunno. i thought it was budiful."

"Stop."

"no? well, okay. maybe thistle make you laugh-"

"Enough."

"what does the letter a-"

"Stop."

"-have in common with flowers? they're both followed-"

"DO NOT FINISH-"

"by bees!"

Flowey's face turned into something horrifying. "If the next words out of your mouth is a pun, you will regret it."

He knew he should stop. He knew he was just asking for more trouble.

But, then, he was probably going to die anyway, right? Might as well.

"i'm callin' your bluff. your bite isn't as bad as your bark."

Before Sans could really register what was happening, there was a flash of green, a loud crack!, a sharp stab of pain in his skull, and then darkness.

⎰Present day⎱

Sans paused in his story, taking a slow breath. It seemed like every word brought back the ache in his bones. He could feel the Corruption spreading through him again, feel Flowey's thorny vine whiplashing into his skull...

Gaster reached out and set a hand on Sans' shoulder, face full of sympathy. "Sans, I-..."

Sans waved him off. "'s fine. not like it was your fault."

"Yeah, but-"

"nah."

"If-"

"nope."

"Sans-"

"i'm not gonna accept your apology and i still have a story to tell, so shut up and listen, dangit!"

Gaster looked a little surprised with Sans' outburst, but recovered quickly, chuckling a little. "Alright, then. If you insist."

"i do insist, thank you very-"

They heard the sound of the door opening. "Dad? Sans? Are you here?"

Sans gave Gaster a look. Later.

"yeah, pap, we're in here."

Papyrus walked into the living room, looking worried. "After school, I went to the lab, but you weren't there, and then you weren't answering your phones..."

"aw, jeez. sorry, pap. guess we got pretty distracted."

Papyrus's expression changed to admonishment. "Did you even go to the lab today?"

Gaster laughed. "No."

Papyrus let out a frustrated sound, stomping one foot. "NNNYYYEHH!! YOU TWO ARE SO LAZY!"

Sans just laughed.

§

A/N

So there's that. If you missed it earlier, welcome to the Retrospect story arc. :D

Anyway, thanks for reading, and I hope you enjoyed it! Remember, votes and comments are not only always welcome, but always appreciated, too!