"Oh God!" she moaned, "I wish I wasn't doing this experiment now, I really want to fuck so bad!"
He could barely contain himself as he saw her open her pussy lips to him. He wanted to have his cock inside her pussy so badly he could not stand it. And the twitching was driving him crazy with ache and increasing is need for release. His cock decided it would be better to speed up his twitching, to make him more horny, and soon he was twitching as fast as he could!