I'm going to stay at my girlfriend's house with her parents' approval. My girlfriend and her sister were in the same room with a bunk bed, but I couldn't stop my lust, so I started having sex quietly without her noticing. While I was pistoning without making any creaking sounds... I found out that her sister, who was supposed to be on the top bed, was peeking at me from her sister's blind spot!! And she even beckoned to me and invited me...! I pistoned slowly, and her sister didn't notice at all, so I signaled to her sister and ejaculated inside her! This time, I got into her sister's futon and had sex quietly! A dreamy second round of continuous creampie with her sister in one night!