Naughty Step Bro

Your step-sister wants your help with her coursework, but she knows you've done this type of coursework before and cheekily asks if you can just do it for her. And in return, she'll make it worth your while, and tease you with her upskirt which she catches you looking up every now and then. She'll even let you get your cock out and wank as she bends over for you and slide off her panties...