My adult stepsister, who has never cared about studying, suddenly announces that she wants to attend college. At my stepmother's request, I become her tutor, but she is so hopeless that I nearly give up immediately. Then she proposes a trade: I teach her academics, and she teaches this bookish virgin everything she knows about sex. Each of us excels in a different subject, so our mutually beneficial secret private lessons begin. An adult stepsibling role-play.