Then she asked me something that I have dreamed she would ask me. Did I want to go skinny dipping with her again? After she took off all of her clothes, she looked down and realized that I had a huge boner bulging out of my shorts! My little sis couldn't have been any nicer about my growing situation. She calmed me down, and reassured me that she wouldn't tell anyone of my reaction. She said it was normal for a guy to react this way to a naked girl, even if it was his own sister.
Then she explained that since I was hard, how it would be a shame to let it go to waste. Besides, she was always curious to see how her big brother's cock looked and how it felt!