It doesn't matter if your best friend is the opposite sex or the same sex as you; as long as it's a close friend, you have hidden feelings for them. People in best friend porn are usually in a friendship and want to try something new at the same time or are both very horny at the same time and place. Best friend porn is mostly just a subgenre of a more well-known form. As an example, think about gay or lesbian porn. Gay porn is known for having friends or best friend porn, in which two friends are left alone and get close and horny with each other. It happens a lot in gay porn because people of the same sex are often friends in real life and don't want to think or say that they fantasize about each other in bed at night. As long as the industry has enough clips for both straight and gay best friend porn, you can choose to watch either type.