The honor student sister was precocious and learned how to masturbate early. The first time she made her brother lick her anus was in the summer when she was a high school student and he was a student... In the end, this habit continued even after they became adults, and even though she had a boyfriend, she couldn't get off without her brother licking her anus, so she went into the forbidden realm and even sought sex... A brother and sister with the best physical compatibility.