Agreed to walk down the street only after having sex with my stepsister

Half-sister in the morning raves about the cool weather and offers her brother to take a walk outside. He does not mind, but on condition that the sister has sex with him. She says that there is no time to waste and offers to have sex with him. In the end, she so irritates the guy that he cum on her skirt and the girl plans to go for a walk in this outfit.