Włożyłem to w dupę mojej przyrodniej siostry uczennicy

One day I visit my best friend at his house to talk for a while, but the moment I get home he goes out to the store and leaves me alone with his stepsister. He entered her stepsister's room and told her to fuck while we're alone. She says yes, but that she put it up her ass since she is afraid to do it through the vagina because she is not taking care to prevent a pregnancy.