Its not that you hated your BFF or wanted them to suffer - but your best friend's sister was so cute and well so was his GF - could you really pass up the chance with both of them? Maybe your best friend will never even know you used their sister and GF
After My bully had his fun with my mom and sister, his next objective was to make me his personnal slut as well... I think it was not such a bad idea after all !