Uphill - Faithtale AU (Sans x Frisk)

When Sans gets the opportunity to pursue his dream job under a famous scientist, he takes it, like any sane person would. The first few weeks, everything is great, until he catches on that something isn't right. -------------------- Credits: FaithTale AU belongs to @momoishy​ and @smollvivi​ on tumblr.
Undertale belon...