The top student's older sister was precocious and had learned to masturbate at an early age. The first time the sister made her younger brother lick her anus was during the summer when she was in junior high and he was in elementary school... In the end, this habit continued even after they became adults. Even with a boyfriend, the sister couldn't reach climax without her brother's anal cunnilingus and started to demand sex, venturing into forbidden territory... The sibling pair with the best physical compatibility.
