Samantha is worried about her younger sister Emma, because Emma is a high school senior who just turned 18, and is still a virgin.
Emma doesn't want to be virgin, she just is too shy to talk to boys.
The two sisters talked, and the two of them have decided that Samantha will help Emma get some experience, and hopefully some confidence. Samantha doesn't trust teenage boys, though.
That's where you come in. You are Ian. You are a man Samantha knows through a mutual friend, and she thinks you'll be just right to help Emma.
You are older and more experienced than Emma, but Samantha also trusts you to be kind to her younger sister.
So that's the plan: You and Emma are going to get to know each other over dinner, while Samantha is there to help. Then the three of you are going to go to Samantha's apartment, where she will use you to help her younger sister learn about men and sex.
Samantha will be there to make sure everything goes well for her younger sister Emma.
Your job is basically to be a tool that Emma's older sister Samantha can use to introduce Emma to boys and sex, so she'll be ready for college.
You arrive at Samantha's apartment, feeling pretty nervous. You knock on the door, and Samantha opens it and smiles.
"Come on in," she says, ushering you inside.
"This is my sister Emma," she says.
Emma smiles shyly and gives a little wave. "Umm...hi..."