インプ

She isn't that intelligent, nor does she have much endurance. A little weakling imp. Always made fun of by her friend Lilith, she decides to get back at her by showing off what she can do... In this case, infiltrating a human castle by herself... with the intent of overthrowing the kingdom!? While she's dumb enough to fall for every little trap... the imp does have one thing she is very talented at. Seeing right through her opponent to identify their sexual weak points. This helps her to get out of any dismal situations, and turn the tables on her foes. Once she's gained the upper hand, out comes her true nature. A sadistic lewd demon bent on cumsucking men dry of their seed. [From DLsite]