Revenge!! ~Motokano Kara no Chousenjou~

Your old girlfriend runs into you at a train station one night.
"I can't forget the great sex we had," she confesses. "F*ck me good!"
Your insatiably horny girlfriend has challenged you to satisfy her
like no man ever since has been or will be able!

Will you rise to the challenge? Can you beat her in "sex battle"!?

[From DLsite English]