Bill almost had a heart attack when he heard the mention of the demon. If he could have a heart attack, that was. Could a dream demon in an artificially made body have a human heart attack?

Thankfully, his cover he made seemed to hold up. Good thing he kept his state of existence under the wraps, or else his task to get that equation from this skeleton would have been shattered. It was on track so far, Sans was easing into a comfortable life with Bill, so he wanted to keep that going. Stick to his plan.

At least, that's what he originally wanted. And what he was working towards. Except for, some reason, he was growing attached to Sans. In a weird way. Like he'd get excited whenever he saw him. Not in a 'there's my victim of manipulation so I can work towards taking over the world' type of way, but in the way that he was simply happy to see Sans.

Bill liked weird. He was born from madness, so were his demon friends, but this was too weird, even for him. It wasn't weird to be weird, it was weird because... it was normal. If that made sense. Bill was supposed to be weird, supposed to be confusing and send the world into chaos. A situation that was normal to mortals was weird to him, but that was because it was a life he simply never lived.

According to human romance stories... Bill was falling in love. With the person he was supposed to make fall in love with him.

Or, visiting the previous topic, he might actually be having a heart attack. That explanation sounded better.

He had to admit to himself, at the end of the day, that he was getting rather used to Sans in his life. His puns were pretty clever, and his witty sense of banter allowed for Bill to easily get lost inside of a conversation. He was small, and oddly cute, with a big smile and - okay, yeah, Bill might have a bit of an attraction to Sans. But he was going to continue the plan. Who's to say he couldn't have both Sans and the entire world? If he conquered the entire world, that'd include Sans by pure definition.

But it wasn't just Sans he found himself enjoying. Of course, Sans was obviously his favorite, as he didn't anticipate all of the settings he made for the skeleton to fall in love to also work in reverse, but he could deal with that. The other mortals, though, were also fun to be around. Papyrus was a hoot, his sheer weirdness complimented Bill rather well. Undyne was hilarious, and Alphys even had a few anime to speak of that got Bill addicted to the media. Gun laser swords? No wonder Soos liked it, they were awesome!

Right. Soos.

That was something Bill had to be on the constant watch for. His advantage of their ignorance would only last as long as he managed to uphold it. He kept the same name as before, so he had to sometimes point out his full name was Billy just to ease any new person he met. To convince them that yes, he totally wasn't the triangle demon and you could trust him. Dipper himself was paranoid, and when he met Bill and heard the name, his body froze up and he stared at him widely. "It's short for Billy, I just moved in from Idaho as Sans' roommate. We'd been messaging for a few weeks beforehand." The mention that he was from a different state and had the papers to prove it eased Dipper considerably. The papers were falsified, of course, but Bill did it much more convincingly than that old man before. He was trying to trick a scientist after all, not some curious tourists. They had to be pure perfection.

"So you guys are going out?" Dipper asked.

That was a problem Bill had to face. That Dipper and Mabel, the two twins that were a constant thorn in his side liked to visit Alphys often and help her with her projects. Even after their weird summer before, they seemed to still like some work with weird things. Helping the monster scientists wasn't out of their field. It'd be fine within itself, Alphys provided a good distraction for Pinetree and Shooting Star, but Sans was one of her closest friends. Which meant he'd often bring Bill over to hang out.

"I guess, yeah." Sans looked away with a blush.

Seeing that face alone made his stomach feel fluttery, and make their held hands feel warm. Kind of stupid, on his part, expecting all of the romantic gestures set to make someone fall in love to not backfire in returning those feelings. Demons, while rare, could find themselves becoming attached to certain mortals. Bill was another victim of the attraction.

"We're officially boyfriends now!" Bill said, leaning against Sans.

"Only after a few weeks?" Dipper looked less anger over more concerned. Mabel definitely did make the boy cautious about fast dating after the whole gnome incident.

"It's called true love!" Mabel roared, sticking her arms into the air. "And if he didn't take Bill, I would have. Because... muscles." She giggled.

Bill held back a roll of his eyes, ignoring her practically drooling gaze at his firm, muscled arms. It was fun to tease her with the unobtainable fruit that was his created human body, but now it was getting annoying. He wanted Sans to look at him more, not some child.

"We are soulmates! Maybe that's why it's working out so well!" Bill said.

"Heh," Sans said.

It became an inside joke between them about the whole soulmate thing. Naturally Sans didn't believe it, because it was a pile of lies Bill made up from poorly filmed romance movies, but it did seem to be working a bit with Sans. Without any other explanation to a shared dream, he did allow some sense of possibility to be believed.

And it was cute whenever Sans would become embarrassed at the possibility of being his soulmate, ducking his face behind the fluff of his hoodie when it was seriously spoken.

The day pressed forward, and Bill spent time with the people. When Dipper and Mabel weren't trying to thwart his plans or kill him, they were fine to be around. Not great, simply fine.

He was sent into the kitchen to get plates, as everyone was going to have some leftovers slices of a pie some goat made. Bill hadn't met her yet. With a sigh, he whipped his hand absentmindedly as he brought down plates with glowing magic, engulfed in blue flames. He just wanted to head home with Sans, really. He liked it when they spent alone time the most.

"Guh -"

Mabel. He knew that slick, intake of a breath as she was caught off guard. The high pitched squeal of confusion.

Fuck.

Surely enough, she was standing in the doorway, empty cups in her hands as she stared at the discovery.

"Wait, no no -" Bill said.

She tried to scream, but he quickly slapped a muffling hand over her mouth. Her running attempt was also futile, much like how she tried to reach for her grappling hook. He used his magic to drag her over, closing the door as normally as he could to not draw attention.

"No, no, Mabel, calm down!" Bill said, "I'm not going to hurt you!"

She made muffled arguments towards him, squinting her eyes as she licked his magic.

"Ew, Mabel spit!" Bill said, withdrawing his magic and shaking it to try and get rid of the liquid.

"You're Bill Cipher!" She hissed.

"Yeah, I know!" Bill whispered back.

"You didn't die when we killed you! Grunkle Stan sacrificed his memories for nothing!" She leaned forward threateningly, or at least tried to.

"He did kill me for a bit, but I was burned with the memories. You brought back the memories, so you brought back me." Bill said, "I cant believe Sixer wasn't smart enough to understand that."

"Hey!" Mabel tried to kick him, but he moved. "When I get out of here I'm going to -"

"Mabel, I'm not here to hurt anyone!"

She froze, caught off guard by his words. A lie, but he had to go with it. She was trusting. Trickable. He had to get her on his side.

"I'm not. I swear." To even prove his lie, he set her down with his magic, then slowly released her from his grip entirely. She didn't run, but looked ready to scream at the first sign of danger. "That's why I'm pretending to be a human. I didn't want to scare anyone."

She glanced back towards the door. "How can you even access our world? I... the rift... didn't it close."

Bill sighed, making a look between guilt and sadness on his face. "It didn't. You guys didn't close it at all, it's still wide open. I healed up after our fight and came back this summer." Now he wasn't even lying, it was true.

"Did you... you're dating - you and Sans!" She jerked a finger to point towards the closed door, "Did he make a deal with you?"

"No, he didn't. He doesn't even know I'm a demon." Bill crossed his arms, making a show of closing his eyes with sorrow. "I wish I didn't have to lie to him, but Sixer already told him about dream demons, and I didn't want to scare him away. Sans is why I'm here. And I didn't lie about us dating. It's not a cover for me, I am genuinely dating Sans."

It took a moment to click. But once it did, Mabel's jaw dropped. "You actually like Sans? Can demons even like people?"

"I'd say more fell in love with... I'm not sure how it happened." Not a lie either. Bill wasn't even sure how he managed to do that, but he did. "And demons can. It's rare, but it happens. I love him, I really do."

"You..." Mabel looked conflicted between her distrust will Bill and her cheesy love for forbidden romance stories. "You fell in love with a person and came here to pretend to be a person... to be with him?"

"I know, it sounds stupid, but Sans just had that charm to him. I wanted to get to know him. So I created this body, and created a story to get close to him. I didn't mean to scare you, and I don't have any plans to try and hurt anyone again. I just... I just want to be with him. He's funny, cute, and I do want to spend the rest of my life with him."

The rest of the worlds existence with Sans as his Queen, but she didn't need to know that.

This actually worked better than he originally planned. Sans was a Quantum Physicist, and having one by his side would be a major advantage. And, by having another ruler by his side that he did love, he'd be able to share his ruling with someone. Power was worthless if he couldn't brag to someone about it. He could have wild parties every night, for all eternity, and spend it with Sans! Show him to his friends, maybe put him inside of a cute outfit, rule the world with him! With unlimited ketchup, of course.

"Oh my god, that's adorable," Mabel gushed, pressing her cheeks together. "This is even better than the vampire human romance I wanted! A mortal and a demon, a forbidden love! Ack, that's so precious!"

"Can you promise not to tell anyone?" Bill asked, cupping his hands into a pleading motion. "I haven't tried to hurt anyone, I'm just trying to be with Sans. And if anyone finds out who I am, you guys will seal me back into the demon realm, and I won't ever be able to be with him."

He was, in a sense, pleading. He could knock her out, or simply kill her, but it'd raise suspicion his way. And he didn't have the equation yet. He just needed to get the equation, to get Sans to fall in love with him even further.

"... Fine!" Mabel huffed, pointing at Bill. "Only because this is romantic and adorable!"