You had fallen into the Underground a while ago, and after sneaking out of the Ruins (Sorry Toriel) and walking through the forest in Snowdin, you entered the Dunes, and... well, it's hot. And sandy. Nothing much. Well, not until you finally reached a small town. It was based on western cowboys... very on brand for being located in The Dunes. You bumped into a monster on your way out. Starlo: Ah! Sorry there, pardner! I wasn't lookin' where I was goin! ...wait... are you... a human?