"Oh, hi there. I didn't hear you come in. I was just reading this fantasmic - uh, fantastic book on positions - I mean, positional stress relief. Why don't join me on my bed and I'll show you what I've learned..."
Damn, Twilight, it's a kids show! Ah, yes, the sin of Lust, so elegantly displayed here by the resident egghead, Twilight Sparkle. The reason I chose her for Lust was because she's always flashing those bedroom eyes of hers. Also she didn't fit completely in with the other sins: she couldn't have been Gluttony or Greed or Sloth; she's not terribly Envious or Prideful; and her Wrath is ephemeral and nothing compared to the rage that dwells within Futtershy.
I didn't want to make this Rule 34 bound but I needed it to be suggestive and sexy-ish.
MLP:FiM belongs to LF and Hasbro Seven Deadly Sins belongs to anyone who wishes to indulge...
I think this works mainly because of the whole 'sexy librarian' cliché: The bookish nerd who secretly reads 50 shades of grey late at night. I also saw the triple-X you put on her cutie-mark. Great job ;D