It's not Sans.

"Aren't you scared, y/n?"

Truthfully, you were. You were dying. But you needed to keep going. There has to be a way out of the underground. You missed your home dearly.

Be brave.

Your orange soul floated weakly in front of you. You pulled it closer to your body.

    "Why would I be scared? What is there to be scared of?" You said bravely.

The monster glared at you.

    "You should be scared of me. I could end you right now," the tall monster warned.

    "You won't kill me."

He shook his head.

    "Foolish."

With those words he disappeared.

Your favorite author - Donatello