When my dad remarried I got a new mom and sister. We were the same age and also had to share my bedroom. My dad bought a bunk bed and I was allowed to be on the bottom bunk. My step sister, Marcy, was a good-looking girl and it was tough having her in my room because before she went to bed she wore almost nothing but a long shirt.
It was a few months after they arrived when my parents went on vacation leaving Marcy and me home alone. I went to our room and when I walked in Marcy was on my bed with my jock strap to her nose and masturbating. I was shocked and soon had a hard cock and when she saw me she smiled and told me she had been waiting for this moment.
Marcy stood in front of me naked and asked me to strip. I did and my dick jumped out and was sticking straight up. Marcy came over and took my hand and lead me to the couch. We sat across from each other and Marcy started to masturbate again. She asked what I was waiting for so I started to stroke myself. Seeing a girl masturbate sent me into a spin and in a minute I shot out my cum. Marcy rubbed quicker and soon had her own orgasm. She came over to me and put her finger in my cum and licked them off. She then put her finger in my mouth and I licked her finger dry. We did this all week long.