"Sans?" Frisk ran after the skeleton, who had already teleported outside. He'd stopped running, and was slumped against the side of the house.

"Sans? Sans! Oh Sans. I'm sorry. I shouldn't have been in your room, let alone snooping around in your drawers..." Frisk said.

"It's okay, kiddo. I wasn't ready for you to see that yet. That's all" Sans replied. Then, he teleported back to his room, and locked the door.

Later that night, Frisk wrote her own letter to Sans and slid it under his door.

When Sans read it, he couldn't believe what he was seeing.

To Sans,

I had to get Papy to help me write this because I fell down here before school taught me anything important.

Anyways... I like you too. You're cute. Papyrus is now telling me "HUMAN! THIS SPAGHETTI IS GOING COLD! GO TO BED SO I CAN DRENCH IT IN ... " and I need to go now bye Sans

-Frisk x

At the bottom of the note, there was a stain. After a moment of confusion, Sans realised it was ketchup, and smiled. The red liquid reminded him of the time that Frisk had tried eating ketchup, and had nearly choked. Then, she had to stay the night, because she was too ill to go home. After the ketchup incident, that night, Sans couldn't sleep, and was contemplating why Frisk would want to drink ketchup, when Frisk walked in. She was scared, as she was sleeping on the couch. Sans let her slip into his bed, and they slept together. It was a good weekend together.

He looked at the note again. Sans couldn't believe his luck! Frisk liked him, and Papyrus hadn't forced him to eat any spaghetti (yet). It seemed like everything was going how he wanted!

That was, until, he saw Mettaton ex lying on his sofa, with his head in Papyrus' lap, whilst Papyrus blushed a shade of orange that was slowly verging on becoming crimson...

It was always obvious they had a "thing" for one another, but Papy had always been so light-hearted about dating, and had always been apparently straight. Sans then realised how little he knew about his own brother, and saw the skeleton lean down and kiss Mettaton ex, just as Undyne burst through the door, wiping tears from her eyes.