An alternate universe of the game UnderTale containing almost everyone as lust filled monsters, and Mettaton EX as a shy talk show host.

Large, beautiful breasts that are keep well consealed and initially appear to be much smaller and less impressive than they actually are until unleashed.

Underlust is Au, of undertale where soul falls into the underground but its not the monster's think. So they send it to W.D Gaster to research about the soul and Gaster finds out that, He can eject the lust in monster's, And then every monster in the underground is filled with lust, Including, Toriel, Sans, Papyrus, Undyne, Alphys, Mettaton/Happstablook and Asgore, And then Asriel is in this world, Toriel and Asgore Where happy about there child and then, Asriel dies and turns in to dust, Toriel and Asgore in Sadness, The ashes of Asriel go on a flower bed and the flowers (Which where roses) made Rose and then Happstablook and Alphys meet up in a Human-Fan-Club and Sence Happstablook likes being on stage Alphys decided to build, Happstablook a Robot body (That was a Sexual related body cause of course not) And Mettaton is on stage and got tons of fans, One night though everything changed, After a show Mettaton was Sexually Assaulted and Beaten by one of his "Fans" Sence Mettaton Was badly beaten Alphys Was trying to repair Mettaton, By doing Minor repairs, and giving him glasses. And is a tad-bit shy now. And a Teen falls into the Underground to soon realize that there is sexual reference's Every where. And that where we are now.
Weapons: Toriel/Old police Batons, Sans/A ripoff of Asriel's Swords, Papyrus/Fists, Undyne/Whip, The rest of these are fists.
I'll leave the rest of the detail's to you.

A undertale porn verson. These Things usually destroys the undertale community.

You're better off not knowing.