The story: My Sister Mia
You the protagonist, are an 18 year old that is about to finish highschool. You live with your mother, father and a hot sister (Mia).
The game starts 2 days before the end of school. You are behind in schoolwork and need to catch up on studying to pass. Your parents are going on a trip to France for a week. You are studying late at night when your sister comes home drunk. You try to take advantage of that.