In this AU, Sans is homosexual/bi-curious, but he can't accept his sexuality.
Underlust is an AU made by NSFWShamecave, who temporarily gave permission to Skele-cakes to continue the AU. NSFWShamecave has since taken back the AU. All the characters are overly sexualized and search for sexual attention except Mettaton who was a victim of sexual assault/rape. Everyone typically wears revealing clothing. Certain locations, such as Grillby's, are also changed to fit the theme.