This is a story about the first time I went to stay over at my girlfriend's house. She has a sister who wears a uniform and has a face that I like, and impressive plump thighs. While my girlfriend was doing housework, her sister tempted me by showing me her panties! Even though I knew that it was taboo to have sex with her sister, I couldn't resist the temptation and jumped into her thighs. By the way, my girlfriend would never let me have sex with her without a condom, but her sister let me have sex with her without a condom to my heart's content V(＾O＾)V.