A brother and sister who met and became close after being approached on the street. The affectionate younger brother shares an apartment and has the surprising secret of still being a virgin! The sister agrees to take part in a sexy project to teach her little brother how to have sex. Tempted by the promise of prize money, the brother gradually becomes more willing. At first, the sister casually explains things while yawning, but soon she begins to feel aroused herself. How will their relationship develop from here? The anticipation builds.