Less than a week after moving in with us my new step sister proudly told me she knew what sex was. I was 14 she was 7 and our parents left me to watch her while they went on a date. We were on the couch watching a movie and a love scene came on. She turned to me said with a proud smiling face she knew what sex was, knew what boys and girls had, and had seen boys penis’s before. I didn’t really know what to say. But she kept talking and it was obvious she knew way more than I did. After talking for awhile she asks if she can see my penis. I didn’t know what to do my mind exploded and my heart was dancing on my tongue. I decided to just go for it and see what would happen and slid my shorts off. She took my dick in her hands and started playing with it. Rubbing the head and stroking up and down. This was the first time anyone but me had touched my dick and I just exploded all over her hands, my stomach, and the couch. When I came she giggled at me and wiped her hands on my shorts. After I cleaned up she cuddled with me on the couch and asked if she could be my girlfriend. Of course the answer was yes. She asked if we had to tell her mom and I assured her we didn’t. And for four years she was my secret girlfriend who gave me my first everything.