Have you been missing your step-sister now that you're away at college? I have to admit that I've been missing you a ton, especially in a certain way. You'll be home for Christmas soon, though. Well, I want to make sure that we have a very special holiday season together. I want us to fuck and fuck for hours, obviously, but I want us to be on the edge of having an orgasm the whole time - until you just cover me in more come than I can even imagine.
Since I know how excited we both get around each other, I think we should practice a little first. I'll guide is through it, so just relax and unzip those pants. I need you to start stroking while I rub my clit and tell you about all the naughty little fantasies your little step-sis has been having about you...don't cum yet! I'm going to bring both of us right up to having an orgasm and then stop, over and over again, until we just want to scream. Trust me, though, it'll pay off at the end.
And you better not cheat, big step-brother! It's hard for me, too - it turns me on so much to tease you and think about you watching my body - but just imagine how much fun we'll be having together very soon ;)