From the site:
"In my opinion a real sex is the mixture of passion and risk. In situations where you are too close to be exposed your feelings are in their culmination. To cut the long story I love a thrilling experience! That day was my debut! I've managed not only to turn all the friends round my finger but even to make my sweet sis believe that I'm her honeyed dream! My poor chick.. Her sound sleep easily permitted me to pretend the boyfriend of hers. Now I know how passionately they love each other."

In other words, make her think she's fucking her boyfriend.