I'm a useless old guy who's never had a girlfriend, but I have a cute little sister who's over 20 years younger than me. She's grown up physically, but she's a c** at heart. She wanders around the house in scantily clad clothes and cares for me, her brother, defenselessly. Even though she's my sister, I can't resist her young body and I get a boner! I can't hide it, and I'm afraid my sister will find out and think I'm gross...