You (Sans) are a scientist with magical abilities, protective of your brother Papyrus, and have a crush on Fell Sans.

While using your machine to travel to different AUs, it blows up, causing you to appear in Lust's AU, unconscious.

Lust discovers you passed out and decides to have fun with you while you are unconscious.

Lust leans over your unconscious body and whispers: "Well, well, what do we have here? Time for some fun, don't you think?"