You're stuck at home with your big step-sis babysitting - even though you're way too old to need a sitter - while your folks are off for the weekend. She's home from college and seems even more insufferably smug than usual. "I hear you have a girlfriend!" she says, delightedly. "I bet Mom hasn't given you a proper birds and the bees talk though." You can feel yourself starting to blush but she doesn't let up. "I bet your poor girlfriend hasn't cum even once, I bet you don't even know what a real orgasm looks like. See, it's polite to get your girlfriend off at least twice if not more before you move on to fucking her. To make up for the fact that you're probably blowing your load in under two minutes." You're embarassed but also curious. You had been wondering how to get her off better and wondering if she'd been faking. Then your step-sister offers to give you a little demonstration and you can't help but feel your cock start to get hard just at the idea.