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Sex and mature themes (including rape and sexual assault) are included in this AU. Do not continue if you are sensitive to themes of this nature.
For a less serious NSFW AU, see Undertail and Under(her)tail.

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.

About this AU


  • All the characters are overly sexualized and search for sexual attention except Mettaton who was a victim of sexual assault/rape.
  • Everyone else wears revealing clothing and some do get involved in some kinks.
  • Certain locations, such as Grillby's, are also changed to fit with the theme.
  • Instead of Flowey being a Golden Flower, he is a rose. His name in this AU is Rosie the Rose.
  • Mettaton is the only character in the underground that is not interested in Sex due to him being a victim of Sexual assault/Rape.
  • It's canon that Frisk looks the same, except their sweater is different color.
  • Asriel was stillborn.


  • Papyrus is still his sweet self underneath, and consoles Mettaton time to time, setting his wants aside, but also still craves sexual attention like the rest.
  • Sans also maintains the hidden depression though his reasons may have changed.


Chapter 1 focuses on the relationship between Mettaton and Papyrus.

Chapter 2 introduces Frisk, and the true beginning of the story.

The rest of the story cannot be told yet.