I ended up having a drinking party at home with my girlfriend and her older sister. When my girlfriend got too drunk and passed out, her sister suddenly moved in close and started seducing me. I care about my girlfriend, but I can't resist her sister's advances. My girlfriend only allows sex with a condom, but her sister is okay with bareback and creampie. Even though my girlfriend is right there beside us, the feeling of being inside her sister without a condom is so good that I can't stop thrusting.