Sans woke up, after a month of dating Bill, in his bed.

His room was pretty bare, decorated with a few select posters of anime Alphys managed to get him into. A computer sat on his desk, closed, and that was the extent of his rooms decoration. Sans hummed, closing his eye sockets again and leaning against Bill's bare chest.

Well, that was interesting.

"Good morning," Bill muttered, throwing a hand over Sans' waist, covered by Bill's blanket, and pressed a kiss against his skull.

Looks like it was official. This was, in fact, a real relationship. One Sans was falling into faster and faster. All Bill had to do was smile and then Sans' soul was fluttering with feelings, he was so far gone it wasn't even funny. But Sans found himself more fine with it, pushing aside the doubt that bubbled in the back of his throat. Bill really did like him.

"I think I love you... for real love," Sans said quietly, stealing a glance up at his boyfriend. "And not just because we had sex, for real kind of love. Like the kind that I want to spend the rest of my life with you."

"I think so as well." Bill shimmied his way down the length of the bed until his face was at level with Sans', pressing a kiss directly onto his teeth that time. "I have to ask you something."

"Hm?" Sans hummed sleepily.

"... Nevermind, I'll ask you later."

So, Sans didn't hear the question.

It was later when Bill asked him a question. Maybe it was the one he meant to ask Sans, maybe it wasn't. "I was wondering, since you're a Quantum Physicist, about what kind of things you could know about. Like the barrier around the town that Dipper mentioned. What is it?"

"Oh, the magical barrier? Yeah, it's a phenomenon in Gravity Falls. I studied it for a bit when I first got here, the old man gave me some of his observations of it. Since Gravity Falls attracts weirdness, it... the best way would be to compare to earths atmosphere. Since Gravity Falls attracts that force of weirdness, the attraction creates an atmosphere to contain the weirdness within the weirdness. It's pretty interesting. Monsters can bypass it, since we aren't the weirdness it's trying to contain."

"That's cool. So you and I can pass through, but the weird creatures in Gravity Falls can't?"

"Yeah. Pretty much. Though it's actually a pretty easy equation to make, since you can plug in some variables to bypass it."

"That's interesting." Bill paused, and slowly turned towards Sans, as if not to startle him. "Could you possibly write it down for me?"

Bill's chest felt cold. He watched, careful.

"Uh... yer know, it's kinda dangerous to leave around," Sans said, "Stan said he didn't want it to ever be removed. In case there's any emergencies."

"For me?"

Silence. Sans stared, then gave such a soft smile it warmed Bill's heart. "Sure. Just keep it safe, alright?"

That's where Bill found himself. In the middle of the night, breathing heavily, with a bite mark on his neck and Sans pressed against his side, asleep. In his hand he clung onto the paper, the equation, staring up at the ceiling. He could have used it the moment Sans wrote it down. Instead they had dinner and had sex again.

His plans were coming together. This would be his break, the homestretch for world domination. Mabel had no idea what he was planning, Dipper was ignorant to his true identity, and the old farts were somewhere on the ocean.

So... why did his chest hurt?

He closed his eyes, listening to the gentle breathing of Sans. His mind through back to the breathy groans having taken place only an hour earlier, the gripping of hands on his own, fingers intertwined, the bite given at a particular moment of pleasure. Then he looked at the paper, again, and felt torn. He... was rather comfortable with the life he developed. A life developed on lies, but so were others.

Bill couldn't get Sans' face out of his thoughts. What he would look like, on the edge of betrayal. When he learned the truth. Was there anyway to convince him otherwise? To pretend none of it was happening? A bubble. Bill could make a bubble.

No, that wouldn't work. Not only was Sans happy with his life, he'd be able to tell when his friends weren't themselves. He'd notice the differences. That's what Bill both loved and feared about him. Sans was smart. He'd notice. Ask questions. Then his friends might come for him, much like Dipper did Mabel. If he did make a bubble, making an entire different world wouldn't work. He should make a smaller one.

Then, with that plan, it wouldn't acknowledge how Sans would feel when he did learn the truth. No doubt he'd feel betrayed. The bubble, if it was small, wouldn't serve as a lie at all. It'd probably be a container to keep him safe.

Bill couldn't trick Sans, keep the false life he held after he dominated the world. Sans would have to know.

Would he be mad? Upset? Angry? Would he lash out and attack, or would he curl up and cry?

One thing stayed clear. He probably wouldn't love Bill after this.

Which was the whole point of this, to make Sans love him so much he'd even ignore the threat of danger to follow him to the end of the world. He wasn't there yet. He also wasn't supposed to fall in love with the skeleton.

Bill looked at the equation. Well, the world wasn't go anywhere. He could spend some more time with Sans. Just a little longer. Try to make him reach that stage of love so Bill wouldn't fear ever losing him.

Because Bill reached that love. Sans wasn't quite there.

Their lives continued after that. Sans would laugh so hard at a pun that he'd spit up his coffee, early in the morning. They'd go on dates, holding hands and trekking up a hill. Sans showed him he could teleport, something only his brother knew. It warmed Bill's heart to see he was so willing to share information. They pointed at the stars before turning towards one another, and right there on the hill became lost in the thralls of pleasure.

Papyrus' diner was doing well. It raised money easily. Mettaton even proposed, so Bill and Sans attended the bachelor party, watching Papyrus happily celebrate the engagement. Bill accidently drank too much, muttering several desires to Sans until he was blue in the face and pushing his legs together. They ended up in the bathroom afterwards, going for a quickie when there wasn't time.

This wasn't working. Bill was just becoming addicted to his human body, to Sans, to their life together. He kept the equation on himself at all times. Even had a backup in the dream realm.

The wedding happened. Sans was the best man, naturally, but Bill was surprised to find himself as one of the wedding planners as well. "Because you're my friend!" Papyrus had said when Bill asked. He almost wanted to cry.

At the wedding, Undyne found herself near Bill, painting at him drunkenly. "So... when are you going to propose, gold hair boy?"

"I..." Bill found no words.

"It's too early! They should at least wait a month!" Alphys told Undyne, before leading her away to properly throw up in the bathrooms.

Sans drove the two home, talking about the wedding excitedly. He was happy Papyrus had a good time, and so was Bill.

"And I'm glad your suit looks so good on you," Sans said, gesturing to his outfit as they stopped at a red light. "Gold and black really do... suit you."

Bill didn't reply, simply dragging Sans' bowtie to him before he pressed them into a kiss. Sans hurried them home, but they didn't even make it past the couch before they were getting handsy.

This wasn't good at all. Bill was falling just as much as Sans was. He was becoming obsessed with his life, and he knew soon, he wouldn't be leaving it unless he took his plan into action. But how could he look at Sans and think about possibly betraying him when he did so many things to Bill?

Bill loved him. He really did.

But it was time.

Bill contacted his demon friends, told them the good news. They prepared. Collected their weapons and magic, ready to escape, but he laid some rules out. They all groaned at the idea of a rule, but once Bill said it, the small change wasn't enough to steer any of them from wanting freedom, so everyone agreed.

Sans stayed under his protection. No touching him.

Bill said he had to stay at home to work on something on his computer. Sans left to Alphys' lab, giving a quick kiss to him before he waved a goodbye. It was time.

The equation worked. Of course, he wouldn't expect any less from Sans.

He even decided to let Mabel and Dipper explain when he started the second Weirdmageddon. Sans had the right to hear from other people before Bill. The demon watched the familiar pyramid rise from the ground, but felt a sickly feeling in the back of his throat. His phone rang, not even a minute after Gravity Falls was consumed by a sky of red, but he didn't pick up.

"Bill?" Sans called out when he threw open the front door, "Oh my Toby Fox, are you alright?"

"Am I alright?"

Bill watched as Sans rushed forward, cupping his cheeks with worry. "I don't know what's happening, all I know was that the sky turned red and some people were getting turned to stone! I came here as fast as I could."

Sans' own phone rang within his pocket. Mabel. Bill could see from his pocket.

"Did you not check in on anyone else?" Bill asked.

"What? Of course I'd check on you! We have to leave, get somewhere safe. I think we can find what hotel Papyrus is staying at and call him on our way!"

Bill stopped Sans trying to leave, looking at him gently. "You didn't even talk to Mabel or anyone else?"

"Oh, crap, I should help them get out of town as well," Sans said, turning to look at the front door. "I didn't listen to Mabel when she tried to talk to me, I was out of the door the moment this stuff happened. But here's what we'll do. You and I can go grab the equation so the demons can't get it, then we'll pick up everyone we can and get them out of town. I think we might be able to -"

Bill tapped the front of Sans' face lightly, immediately knocking him out on contact with a burst of magic. Sans thumped against his chest, and Bill lifted him up into his arms, creating the small blue hoodie bubble around Sans. It contained his body, before getting smaller. Once done, the bubble fluttered to Bill, no larger than a tiny marble. For easier carry.

"You'll stay right here, Sans," Bill said, pressing the bubble against his chest before it formed strings, wrapping around his neck like a loose hanging necklace. "I'll visit you soon. I promise."

Time to take over the world.