My country bumpkin sister is using my penis to practice sex!? HUNTB-648

My sister, who had almost no contact with the opposite sex and attended an all-girls school, was about to attend a co-educational university. Presumably, she was shy after starting, so she asked me, her older brother, to be her practice partner. At first, it was just talking and holding hands, but seeing her unguarded exposure and her chest pressed against me involuntarily aroused me…