Today my girlfriend invited me to her house to play. Her parents won't return tomorrow night, so I can stay at her house tonight. My girlfriend still has an older sister who is on vacation so she is always at home. The first time I met her, I was captivated by her beauty. I heard from my girlfriend that she once won a prize in a university beauty contest. While talking to her girlfriend, Ms. Miu brought a cake, this is the cake that countless men who were pursuing her brought as gifts. My girlfriend immediately went to get the plate, just waiting for that opportunity, Miu immediately leaned close to my ear, whispered lewd words and continuously blew into my ear! She only stopped when my girlfriend returned to the room. After dinner, my girlfriend went to wash the dishes, and she continued to do those lewd acts with me. But this time she was even more daring, she even sucked my cock!!! Then I took a shower with her, and of course she squeezed out my sperm in the bathroom. Being stimulated by Miu, I wanted to have sex with my girlfriend, but because I was on my period, I wasn't allowed to touch her. While feeling uncomfortable, Miu suddenly appeared! She constantly seduced me, invited me, and spoke sweet words into my ear. I couldn't stand her seductiveness so I had sex with her despite my girlfriend sleeping next to me!!! And from then on, I continuously had sex with my girlfriend's beautiful sister whenever she was absent...