For the first time in a very long time, Sans was genuinely scared.

Okay, so maybe scared was too mild a term for what Sans was feeling. Terrified. That was closer to what he was feeling. He was absolutely and totally terrified. He felt like he was about to be attacked at any moment, and he didn't know where it was coming from. Except he did know.

It was Frisk.

She had… kissed him.

Oh god, she had actually kissed him! He didn't even know what to deal with that. He didn't even know how to feel about it! For everything Gaster had done to him, not once had he kissed him. He was just a test subject to him, after all. Just a thing. A sex toy. A brood mare. It had been his first kiss.

God, he sounded like one of those girls in the cartoons that Alphys denied she liked.

It wasn't just his first romantic kiss either. No one had kissed him before. Not even platonically. He never had a mother to kiss him goodnight. Papyrus was more likely to beat his skull in.

Papyrus…

Sans couldn't help but let his mind wonder to his brother. The change in his brother had been… disconcerting to say the least. It's not like he pulled a complete one eighty. He was still rough and angry most of the time. He was still more likely to shoot first and ask questions later. But he hadn't actually dusted anyone since… well since Frisk came. He hadn't laid a hand on Sans either. He still insulted him and berated him for being lazy or for his puns, but his words had lost their edge. They were by no means best friends, but their relationship had become… tolerable.

All thanks to her.

Oh god. Her.

What the hell was he going to do? He had no clue. For the time being, he just did his best to avoid her. He didn't want to. He wanted to be with her every second of every day. Who could blame him? She was so kind, despite what the monsters had done to her. She had died so many times- too many times- by their hands, yet she never held it against them. She was the only one who ever laughed at his puns and his lame jokes. Who wouldn't fall in love with her?
Dear god, he was in love with her.

And now he was even more terrified.

He was so distracted by his own thoughts that he didn't even notice another presence until he felt the gentle tug on his sleeve. He started and looked beside him to find the one person he didn't want (except he did, more than anything he wanted) to see.

Frisk looked up at him with those soft eyes and his soul felt like it was going to melt. She was so beautiful. The words always entered his head every time he saw her. Yet, he realized, she was also nervous. She had let go of his sleeve when she had felt him start. She bit her lip and looked away nervously before raising her eyes to look at him again.

"I… I know… you've been avoiding me."

Sans hadn't heard her speak since their face off at the barrier, yet it was just as soft and gentle as he remembered.

"That's…"

"Are you upset? That I kissed you?" she asked.

"No. I mean yes. I mean… I don't know," Sans sighed in frustration and shook his head. "Frisk… I… this can't happen."

He wanted to take the words back the moment he said them, but he knew he couldn't. It had to be said.

"Frisk I'm… This won't work. The things that i've been through," Sans hesitated, and for a moment, he wanted to tell her everything. "I'm broken."

Frisk was silent for a moment.

"Do you want to?" she asked, her voice almost a whisper.

Sans froze.

"If you don't, just say so. Look me in the eye and tell me now."

He really should. He was going to hurt her in the long run. But he couldn't bring himself to look her in the eyes. He couldn't lie to her. Instead he looked at his shoes.

"Do you remember what I said at the barrier?" Frisk asked. "Do you remember why I came to the underground?"

"You were looking to something," Sans said. She nodded. "You never said what it was."

Frisk took a deep breath before reached for the hem of her shirt and pulling it over her head. Sans' face flushed red. She was wearing a white shirt like the first time he had seen her without the sweater and just like before, he could see the upside down heart over where he human heart should be.

"Do you know what his is?" she asked.

"It looks like a tattoo of a monster's soul," Sans said.

"It's not though. I was born with it. It happens sometimes. It's rare though. The first human Chara had one as well," Frisk said. "It's a soul mark. Humans get them when they have a soul mate. Only about one in a billion are soul mated to a monster though."

Frisk's face darkened.

"Even less survive long enough to find their mates."

Sans didn't like the sound of that.

"So you came to find your soulmate," Sans said. It wasn't a question.

She nodded.

"And you know who it is?"

She nodded again.

"I used to get these visions," Frisk said. "I saw them every time I looked into a mirror. I would see this… monster. I thought I had gone crazy at first, until I found out what it was."

Suddenly, her story was sounding eerily familiar.

"It was my soulmate."

Sans looked away again. He knew where this was going.

"My soulmate should have had similar visions," Frisk said hopefully.

"I don't have a mark," Sans whispered.

"Monsters never do," Frisk said.

"How do you know that?"

"She told me. Chara," Frisk said. "She's still around, you know. Her determination was so strong, she could talk to me and only me. She told me everything. About soulmates. About monsters. About her soulmate, Asriel."

Sans' head was spinning. Everything she said was possible. He knew that. And he knew she would never lie to him. Everything she said lined up. But…

"I know you're scared," Frisk said.

"And are you?" Sans asked. "You've seen what I'm capable of. What I'm willing to do."

You've seen me kill.

"No," she said. There was so much certainty behind her voice that he couldn't help but believe her. "I know you would never hurt me."

"I may not want to, but I still could," Sans said.

"You know the funny thing about soul mates? They are always perfect for each other. They are always exactly what the other needs," Frisk said. "I want this. I want you. And not just because of this mark either. At first, that may have been the case, but now… I love you, Sans. I love your puns and silly jokes. I love how you've always been there for me, even if you try your hardest not to be obvious about it. I love how hard you try to hide how smart or how strong you are."

Sans didn't even realize he was crying until he felt her hand on his cheek and her thumb wiping the tears away.

"Please. Trust me," Frisk pleaded.

Who was he to deny her?