Today I was invited by my girlfriend to the house to play. Her parents will return tomorrow night, so I can stay at her house tonight. My girlfriend still has an older sister who is on summer vacation, so she is always at home. The first time I met her, I was captivated by her beauty. I heard my girlfriend tell me that she once won a prize in a university beauty contest. While talking to her girlfriend, Ms. Miu brought a cake, which was the cake that countless men who were chasing her brought to her. My girlfriend immediately went to get the plate, just waiting for that opportunity, Sister Miu immediately came close to my ear, whispered lewd words and kept blowing 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 it was even bolder, she even sucked my cock!! Then I took a bath with her, and of course she squeezed out my sperm in the bathroom. Stimulated by Miu, I wanted to have sex with my girlfriend, but because I was on my period, I couldn't touch her. She was uncomfortable when Sister Miu suddenly appeared! She kept seducing me, inviting me, saying secret words in my ears. I couldn't stand her charm, so I joined her in the rain despite my girlfriend sleeping next to me!! And since then, I have been constantly having sex with my girlfriend's beautiful sister every time my girlfriend is absent...