At home with your girlfriend's hot sister

Tomorrow my girlfriend goes on a business trip, so tonight I'm going to her house to sleep the night. In the house, Tsukasa Aoi is her younger sister, a very hot girl. The next morning, my girlfriend left early, I woke up later and hurried back home. But when I got to the door, Tsukasa Aoi called me. She had just finished showering and was only wearing a towel. What does Aoi mean, I will get to fuck her.