I think that Renrink & Blackaerin made this AU. If not, Toby Fox made the original, "Undertale".

(Your POV)

My name is (Y/N). I am a water nymph. I was raised by Toriel, Goddess of Life. I mean, technically, I still live with her but whatever.

Anyways, Toriel asked me to go to the nearest shop to get food and clothing. As I exited the RUINS, I was hit with a bit of a chill. I forgot how cold SNOWDIN was. Then I heard the stick crunch. "Sans, it's me. (Y/N)."

A short skeleton with a black robe and scythe jumped down from the tree. He was grinning. "Aww come on (Y/N)! Let a skeleton have a bit of fun."

I smiled cheekily. "Never."

"I guess your funny bone will remain broken for the rest of your immortal life."

I laughed. "Anyways, I got to get to SNOWDIN quickly. It looks like I might have to stay the night at the Inn."

I knew the regular offer was going to come sooner or later. "Y'know (Y/N), you could just sleep over at our house."

I shook my head. "Nah. It's okay."

~Time Skip - Next Day (After Shopping)~

I was walking back to the RUINS doors, when I heard something. I looked around, and saw Sans deep in the forest, looking into a pond. I channeled my powers through the pond to hear what he was saying. "I just wish (Y/N) could like a god like me. I mean, I'm the god of death and she's a water nymph! How could she ever love me like I do her." Oh but I do Sans. I love you more than Mettaton loves himself.

I didn't realize I was still channeling the pond until Sans poked my forehead. "How long were you listening (Y/N)?" His cheeks were glowing a pale blue ans gray color.

"Long enough." I hopped out of the pond and kissed him.

In that sudden moment, a cannon went off from my heart.

We finally split away from each other after 1 minute, but was seems like eternity.

I looked him in the eye sockets. "I love more anything else in the UNDERGROUND."

He grinned while his cheeks were glowing like glowsticks. "I love you so much (Y/N). I've loved you since we first met."

We kissed multiple more times.

Let's just say I never made it back to the RUINS that night.