Spending My Birthday Between My Step-Daughter's Legs!!

Every year my wife and step-daughter throw me parties for my birthday. I tell my wife that she really doesn't need to make a big deal over my birthdays but she always does anyways. While my wife decided to go out for some party supplies, I decided to hang out by the jacuzzi. While enjoying the warm bubbles, my beautiful 18 year old step-daughter walked out in her pink bikini and wished me a cheerful happy birthday! I can't believe how grown she is getting, after all....I feel like we were just celebrating her 18th birthday yesterday, even though it was over 6 months ago. Man does time fly! After wishing me a happy birthday, she asks me for a sip out of my cup. My initial reaction was no, but I realize she is getting older and she is going to want to experiment with things. So I tell her she can, but only if she promises not tell her mother, as I don't want her mother to think I'm condoning this behavior! But who am I kidding, I just can't say no to my step-daughter... She bought this incredible book for me, which she didn't have to do! But she tells me that there's more to my b-day gift. Then I watch as her bikini top starts to slip off her petite body! I cannot believe my eyes! She starts talking dirty to me and I know I shouldn't keep looking, but it's impossible to resist her! I was surprised at how developed she has gotten, and how much she craved my cock. She sucked me off so good, I can't believe how much of a dirty little slut my step-daughter could be, but at the same time....I loved it! Once I stuck my raging hard on in her tight pussy, there was no going back. She felt so wet as she slid up and down on my throbbing dad meat. I have to admit, she definitely knows her way around a cock. She even let me finish my load on her face like the good little slut she really is. This has been the best birthday gift I've ever gotten!