Today is the first time I have been to my girlfriend's house to play. That night we were having sex with each other when her sister suddenly opened the door and saw the two of them having sex. I was extremely embarrassed and was going to apologize to her. As soon as I walked to the door, I was able to admire her beautiful huge breasts as she was changing! The next morning, when my girlfriend went to put on makeup and get dressed, she kept using her big round breasts to seduce me, making my little boy quickly swell. Although she likes her girlfriend very much, her sister is too charming! "I may not need to wear a condom when I have sex with you", "I can ejaculate a lot of sperm inside me". She kept seducing me with things I couldn't do with my girlfriend. The thrill of secretly cumming into my girlfriend's sister's pussy made me extremely excited. When my girlfriend suddenly came back and found out, I still couldn't stop having sex with her. In the end, I cum full of her pussy right in front of my girlfriend's eyes!